PLANE on a CONVEYOR BELT! Will it TAKE-OFF? Explained by CAPTAIN JOE

[@Engr.princemamanaoalorro07.1]

Next Riddle: How will the plane land on the Conveyor belt

[@cccycling5835]

Ask a Navy Aviator

[@gamingwithdrelph4962]

It think it just like landing in a moving ship/aircraft carrier

[@cellogirl11rw55]

I don't think so. It would bounce too much.

[@XTR_NEELAN]

That kinda ez I guess if it going opposite

[@tymekthecebula6901]

Hmm

[@shmooveyea]

If I'm on a treadmill on roller skates holding a rope my wheels will match the speed exactly, but if i pull on the rope I move forward. The engines are pulling the plane forward, the belt will not stop the plane from moving forward, the plane always takes off

[@jbt816]

you're assuming the treadmill's speed is always the same. the riddle's premise is that as you pull on the rope, the speed of the treadmill will also increase

[@jagheterbanan]

@@jbt816but that won’t change anything, if the treadmill is going 20mph and you pull yourself forward at 1mph and some increases the speed of the treadmill at the same time you will still pull yourself forward at 1mph. The speed of the wheels and treadmill is completely irrelevant.

[@MrDefreese]

@@jagheterbananyou will pull your torso forward, but the conveyor adapts to the increased wheel speed and still results in the ‘wheel axle’ remaining static. That’s the whole point of the unintuitive example of the conveyor speed matching rolling speed. You would essentially tip over forward.

[@jagheterbanan]

@@MrDefreese The wheels are attached to the roller skates with bearings essentially disconnecting them from you so no you wouldn’t tip over you would just increase the speed by which the wheels are turning. This of course brakes the premise that the wheels and treadmill are supposed to be going at the same speed, the only way to keep that premise is to not move i.e. not pull the rope. If you translate that to the airplane it would mean you can’t increase the thrust, so yeah an airplane that you’re not applying thrust to won’t takeoff but it’s not really because the conveyor belt is stopping you.

[@MrDefreese]

@@jagheterbanan the wheels and treadmill moving at the same speed means the position of the wheel never changes. The force applied by pulling the rope does mean that part of the body moves. We could do fun body deformation experiments with that - rigid body, flexibility at the waist, etc.

[@scullyjr2073]

3:01 Captain Joe: rocket science, math, aviation Me: oooo yellow black

[@ZEM502]

*insert Wiz Khalifa - Black And Yellow here

[@routergray7041]

The issue is the interpretation of 'matching'. The sane interpretation is that 'matching' happens no matter what speed the wheels go, because 'matching' is a functional result of the mechanical contact between the wheels and the conveyor belt. In other words 'matching' means 'synchronizing to' not 'going as fast as'. But, since the rule demands compliance from the conveyor belt, not from the wheels, the interpretation doesn't even matter. If the conveyor belt runs afoul of physics, that is its problem, not the airplane's problem or the wheels' problem, thus the plane will happily ignore the logic explosions consuming the treadmill and take off regardless.

[@wl6558]

Joe, I’m pretty sure the wheels in scenario 1 would spin up exponentially and presumably explode but don’t think it would have a significant effect on airspeed any more than scenario 2.

[@paolodalbono]

Correct!

[@kristofinportugal]

Exactly

[@nloko]

Scenario 1 is an impossible (and absurd) theoretical/mathematical scenario; v(ground) needs to be >0 to create airspeed, but for that to happen v(wheels)>v(belt) which the text says is impossible (they're alway the same)... both conveyor and wheels will reach infinite speed in t=0 (infinite acceleration) and break the equations.

[@paolodalbono]

@@nloko I agree! Scenario 1 cannot be performed in real world (infinite is not an option in real world), so has no meaning.

[@wl6558]

@@paolodalbono Agreed, but assuming the answer to the riddle is meant to be "Yes." or "No." rather than "Exploding infinity tires." - and keeping in the spirit of the problem - even if you adjust the conveyor belt to something reasonable, you still have what the Mythbusters already did in small and full scale. Even if you say the conveyor belt gets to accelerate twice as fast and to twice the take-off speed, right to just before the tires fail - which is presumably double the parameters of what this riddle is asking, the plane still takes off pretty effortlessly.

[@saims.2402]

That’s one big conveyer belt.

[@techmantra4521]

It's made from my belt cause of my lockdown belly.

[@robrod3097]

@@techmantra4521 😂😜 funny stuff kiddo !!

[@brantwedel]

The earth is one big conveyer belt ;-)

[@saims.2402]

@@brantwedel 🤯

[@johnsiders7819]

It did take off BUT if you watch it closely the plane started moving forward before it rotated

[@the_forgotten_shuttle]

Alternate title: Can plane on conveyor belt destroy landing gear of the plane?

[@LERobbo]

Alternate ALTERNATE title: can you find a conveyor belt big enough to fit a plane?

[@vncxdy]

Yes, it can.

[@omarjones1460]

Who cares. We're talking about a 747 on a treadmill. Just imagine the wheels can take the forces.

[@carultch]

Yes. The bearings in the landing gear will break their rolling elements if the wheels spin too fast. The centrifugal effect causes the rolling elements to load the contact force between the outer race and the rolling elements, and when that contact force exceeds the limiting strength of the materials, the rolling elements and outer race will rupture.

[@usedcarsokinawa]

It’s the wind going over the wings that causes lift, irrespective of the wheel speed.

[@stevehackett2678]

I think this guy is wrong. There would be No wind over the wings, If the conveyor belt moved at the exact same speed as the wheels. The plane Has to move forward, in relation to the ground, to get lift. As long as the plane is On it’s wheels, the conveyor belt would negate its forward motion. If not, why do planes even need runways? Could just build a large dynamometer, and planes could take off without moving forward.

[@perendinatorian]

@@stevehackett2678 it's more the case that a plane will act as if the conveyor isn't there. when you drive a car the engine moves the wheels along the road. when you fly a plane it move the air through the jet or propeller. you have to imagine that the air is the planes' road and the mode of propulsion is the wheels equivalent .If say instead of wheels a plane had skis and a flat icy surface, it'd move forward and eventually take off as normal.

[@AB-80X]

@@stevehackett2678 The plane is not "fixed" to the wheels due to the bearings. The wheels are not the driving force. No matter how fast you spin the wheels, the engines will still see the air as standing still and thus create thrust. If you have thrust, you have forward motion. It's a plane, not a car...

[@SteveDPIves]

@@stevehackett2678 You’ve basically just restated the problem. But the conveyer belt moving backwards (and the wheels spinning backwards) has no effect on the plane’s forward motion, as the forward thrust is provided by the engines and not by the wheels.

[@julese-p278]

@@stevehackett2678 The plane does NOT have to move forward in relation to the ground in order to get lift, it has to move forward in relation to the AIR. So regardless of what it's wheels are doing it will still move forwards and gain lift - just as it normally would. It will travel the same distance forwards, and it will rotate at the same point it normally would. The ONLY difference is it's wheels would be spinning faster than they usually would, that is all.

[@FivePointsVids]

Thrust

[@kingkenny97]

Not before you touch up with Manscaped!

[@tymekthecebula6901]

@@kingkenny97 haha

[@shedeur]

thrust

[@chinocracy]

Only if it's VTOL, lol

[@cm5754]

@Buddy Austin The wheel bearings prevent the conveyor from imparting backwards force on the plane, but the engines still accelerate the plane forward.

[@sdm5906]

“ the only 747 that can do that is the captain’s joe 747“ I liked that part 🤣 You’ve become a good commercialiser

[@guessmyhandle]

If jet engines are pushing left, the conveyer pushing right, the wheels are just bearings and play no affect.

[@jrunsvold7150]

Ever heard of friction? As soon as you try to move forward the conveyor counters it so you would never move

[@Xiaotian_Guan]

@@jrunsvold7150 Right, friction is the key. I'm really frustrated that neither those arguments nor those counter arguments is taking friction into account, which is the only way to make things clear. But to cancel the thrust of the engine, we need the same amount of friction, which I don't know if is actually possible (something tells me this is not going to happen in real life. I would still call this theoretically possible though.)

[@KillarneyMark]

@@jrunsvold7150 ever seen a travelator at an airport? Think you could push a trolley along it in the opposite direction? Of course you could. It just needs enough power.

[@imthedarknight-8755]

@@Xiaotian_Guan problem is the plane has wheels, and in an ideal situation (which is fair to assume since we have a conveyor belt the size of a big ol plane) the wheels are frictionless so the movement of the wheels exerts no force on the plane itself, it just spins the wheels. The wheels can't exert a force on the plane, so therefore it doesn't hold it back at all

[@jrunsvold7150]

Nothing can be frictionless. Otherwise nothing would exist at all

[@lukeheasman350]

With this logic on the conveyor belt, it doesn't mean anything as you could ramp the conveyor up to 10x the speed of the plane in the opposite direction and yet the plane would still move forwards

[@MrDefreese]

@@lukeheasman350the conveyor only moves the exact distance the vehicle moves. Not more, not less, not faster, not slower. The wheel axis never moves.

[@user-xu9bq2lf6p]

@@MrDefreese the wheels dont have anything to do with plane moving forward with thrust

[@MrDefreese]

@@user-xu9bq2lf6p yes they do while it’s on the ground. In fact, all thrust does is take the body from one speed to another speed (less any losses).

[@user-xu9bq2lf6p]

@@MrDefreese the wheels just spin and thrust moves it forward

[@MrDefreese]

@@user-xu9bq2lf6p yeah, that’s an inadequate understanding of wheel motion. In your mind, do wheels scrub on the surface or do they roll on the surface. Either option give you the speed at which the test vehicle moves which is exactly the speed the surface moves…therefore you get 1-1=0.

[@stmounts]

The 747 can only take off if the airflow over the wings is sufficient to provide enough lift. So the 747 must move forward at takeoff airspeed, regardless of the surface being a runway or a conveyor belt.

[@andrewong2956]

Because the plane gets enough AIR-speed to take-off. The jet engines propel the AIR to move forward just like jet fighters.

[@yjk2202]

👍@stmounts You have put your finger on the pulse when you state that relative movement of air over wing surfaces causes lift. The conveyor belt and engines are not the elements which generate lift. Only the foreward motion of plane (with the help of the engines, etc) generates a pressure differential on 'curved' surfaces to create lift. How else does

[@yjk2202]

a glider stay aloft ? And Why do aircraft carriers use catapults to get off the deck?

[@waddup2336]

@@yjk2202its so enough air to pass through the wings to generate lift.

[@wizardoftehtime]

@@waddup2336 Your understanding of how lift works vs thrust is not even close to how it actually works, if the plane moves the throttles forward and the wheels start to move from the ground speed of the plane starting to move, but then the conveyor then perfectly matches the speed of those tires for ground speed, so no the plane in no longer moving forward or backwards, how to the planes wings which have to have airspeed flowing around them to produce lift, produce lift if the plane is not moving at all on the ground so no lift is being produced by the wings? When the engines produce the thrust to get the plane moving on the ground to speed the plane up so the air around the plane is producing lift on the wings, the ground speed is then completely stopped by this conveyor that now puts the planes ground speed to 0 which then means there is no airspeed being produced for the wings to create lift. Just because the engines of a plane done care what happens on the ground does not mean that the wings can produce the lift from having no airspeed to then convert to lift as the plane that is on the ground has to have forwards movement to create the airspeed required for the wings to get the lift needed, but if the forward movement is 0 because the conveyor is now keeping the plane still, which makes the airspeed 0 over the wings, which means 0 lift is now being produced to have the plane take off.

[@marionette5968]

The real question to answer here is "how does the airplane stay flying once the wheels are off the ground?" Once you know the answer to that, its easy to work the problem out.

[@kristofinportugal]

The plane is pulled forward by the engines. Once you reach a high enough ground speed, the plane lifts off. Independent of underground and wheel speed. Although the wheels would in this case explode.

[@Psyrecx]

The real question is something you'll never understand, because you couldn't read it in the first place.

[@c182SkylaneRG]

Simple thermodynamics, my friend. :) All mechanical systems boil down to energy in = energy out. In this case: thrust = friction. At infinite speed, the friction of the wheels will remove infinite energy from the mechanical system. Also, the conveyor is defined as matching the speed of the wheels. Any forward movement of the airplane with respect to the ground violates this definition.

[@nicolivoldkif9096]

@@c182SkylaneRG incorrect, if your going to try to pull that crap then you failed. Under no point in the question did it state the rotational speed of the wheels. Therefore the only logical assumption is that it is match the forward motion of the wheel itself. Your trying to selectively add things into the question. If I asked you the speed of a tire that broke lose from a moving vehicle noone would give you its rotational speed. This is a common issue with technically educated people and commonly worded questions. You destroy the spirit of the question by adding in stuff not present into the question. I mean why would you add in that if the pilot would apply a little bit of steering then you'd have wheels moving at different RPMs and the belt would therefore enter into a paradoxical state where it would need to be moving at multiple speeds at the same time. Basically this is equivalent to the mathematician that argued 2+2=5 could be true because it theoretically could be 2a+2b=5c or maybe some other hidden or non presenting variables or perhaps a variant numerical system.

[@c182SkylaneRG]

@@nicolivoldkif9096 The term "wheel speed", lacking any other description, means the speed of the wheels across the ground, which is taken at the hub/axle. In this scenario, that would be the speed of the wheels relative to the conveyor belt. Their rotational speed is translated to a linear speed based on their diameter, which can only be in reference to the surface they're rolling on (the conveyor). Any good pilot starts on the center line of the runway, and stays on the center line of the runway. No self-respecting pilot takes off cock-eyed with respect to the runway centerline. Be realistic. :D

[@MistaJayRo]

The answer is in airflow over the wings, wich generates LIFT. Flying has NOTHING to do with wheels.

[@ntsecrets]

Actually it’s the airflow under the wings - Newton’s 2nd law. That’s what gives it lift.

[@r_v_t]

@@ntsecrets agreed, but in any normal GA plane, how Mitch does it account?

[@calumryan6328]

Something that’s not clear is where the lift is coming from, are the engines sending air under the wings or are they pushing the plane forward which makes air rush over them to create lift?

[@PeterNGloor]

@@ntsecrets I heard otherwise.

[@ASVPChrisB]

@@ntsecrets Not really. Most lift comes from the negative pressure over the wing. Bernoulli's theorem applies, not Newton's Second Law.

[@Money4Nothing]

The riddle is that you can't in reality make a treadmill that matches the speed of an airplane wheels. The wheels don't propel the plane, they just respond to the relative motion of the plane with the ground. Which means if you move the ground (i.e. treadmill), the plane or it's wheels don't know the difference. The plane will just move forward through the air not caring what the wheels or ground are doing.

[@royeb63]

My thoughts exactly. The wheels are not what's propelling the plane forward. They are just free-wheeling. As the plane picks up speed, the wheels would spin faster than the plane's forward movement would indicate, but other than that they would not in any way influence the plane's acceleration. Maybe a few tires would blow because they are spinning much faster than their designed limits, but it would not prevent the plane from taking off.

[@benjaminshropshire2900]

A easier to think about situation that is equivalent is placing a trailer on the same treadmill and pulling it off with a car in front. It moves (or the tires explode if the treadmill can go that fast). Now replace the trailer with a glider being pulled with a cable. It starts moving and takes off. And finally an airplane being pulled (or pushed) by it's prop or jets. In all those cases, the thing being moved is being moved by a force applied not though the wheels, so they are basically the same, so the airplane will move as well.

[@AzrealUO]

@@robertwatson818 The engines push the plane forward through the air (regardless of what the wheels are doing). The wheels on a plane are simply free-spinning bearings to allow the plane to "roll" on the ground, they have nothing to do with propulsion.

[@kennethfharkin]

@@robertwatson818 but there will be because the airplane WILL move forward. The THRUST propelling the aircraft forward does not care that the conveyor is moving backwards. The wheels are free spinning. Make the conveyor move as fast as you want, the wheels will simply spin faster until the bearings or tires explode. The plane WILL move forward because the force propelling it will be exerted on the AIR, not transmitted through the tires to the roadway as will a car. Only if the combined friction of the free-spinning wheels overcomes the force of thrust would the aircraft not move forward and again, at that point you would have blown up your landing gear.

[@petersantos6395]

Wheels are not free spinning, they have friction, if the plane is not already flying, the friction will create drag, that's where the first part leads to (however you won't have infinite friction since the pressure downward is constant, is that enough to prevent the plane from take off we simply don't know, because the threadmill would overheat before it can reach that)

[@monteevans7985]

I think this question was thought up to highlight the difference between how a car is propelled down the runway and how an airplane is propelled down the runway. As such it is a thought problem and would work better (less confusion) if it was explicitly idealized. My suggestion is to include in the problem statement something like "consider the wheels themselves to have no friction in their bearings, no rotational inertia, no rolling friction, and no residual drag in the brakes when they are released." (visualize them to be something like a bicycle's spoked wheels with zero mass, and no brakes at all." LOL (also utterly indestructible). The question seems to me to be, then, "how can this conveyer belt runway PULL on this idealized airplane?" My answer is "it can't" - run the conveyor belt as fast as you want, all that will happen is the wheels will spin. The inertia of the airplane (tendency to resist changes in velocity) will keep it sitting there, until the throttles are advanced. With 4 big engines attached firmly to the body of the airplane it would accelerate down the runway with no trouble at all and take off when its airspeed reached the value to start rotation. However, if the wheels are given mass, and the conveyor belt runway is given access to unlimited energy and power, then pulling on the bottom of the wheels will actually transmit some force onto the body of the airplane (as well as give the tire rotational kinetic energy) and with infinite energy and power the conveyor belt would win.

[@ivani3237]

for fair experiment lets take force of the conveyor equal for the force of plane engine. In that case plane take off easily always

[@drabberfrog]

Even if the wheels have only just enough friction from the ground to prevent slipping, the energy it takes to rotate them is coming from the engines. You can't just disregard the wheels because they are stealing all the energy you need to move the whole aircraft forward.

[@MrDefreese]

it is immaterial how the vehicle is propelled. The only thing that matters is that the vehicle only moves while it is on the ground by rolling. If it rolls, they you know the rolling speed and as such you can set the magical, hypothetical, and impractical conveyor to the same exact speed and with the same exact rate of change. People are trying to complicate the simplicity of the thought problem. The thought problem is trying to show that you can't get a plane flying if you don't have airflow over the wings to create lift. You can either do a deep dive four force analysis while it's on the ground and measure the force, the drag, the weight effect on the rolling, etc. or you can take at face value the basic introduction to physics stuff where the velocity of the vehicle minus the velocity of the conveyor gives you a net zero in motion.

[@monteevans7985]

@@MrDefreese My point is unless the speed of the conveyor belt can affect a longitudinal FORCE on the airplane wheel axles, there is NOTHING to keep the airplane from accelerating down the runway as the mighty (777-300ER) engines each apply 115 THOUSAND pounds of force! When the throttles are advanced, without brakes, the airplane accelerates down the runway until it is time to rotate and climb out., at which time it flys off. During acceleration on the runway when this idealized conveyer belt is going like a bat out of hell, it has NO GRIP on the airplane. By the way, something like this was tried on MythBusters using a long tarp pulled backwards and a Cessna going forwards,. The Cessna took off just fine.

[@MrDefreese]

@@monteevans7985 that's not quite right all around. The force applied by the aircraft only results in either rolling speed on the wheel set or scrubbing across the surface. If you have one speed, the (magical, absurd) conveyor is explicitly described as matching that speed (with some equally absurd force). What you have is not just an aircraft floating above the surface with a horizontal force due to its engines. You are dealing with a system that includes the interaction of the wheel set while it's on the ground. You could just as easily use a cog gear set since we are hopefully assuming that the craft is not going to scrub across the surface in this exercise, but will only be constrained to rolling. If you have those meshed gears rotating at the same rate, guess what, there is no net motion. That's what we have. Now, people frequently cite Mythbusters, but they didn't do their experiment properly. You can see that they gunned the truck and gunned the aircraft with not consideration for the rate of change between the two. That's not a proper way to do that experiment. A little known factoid is that they did a preliminary test with a little RC car on a treadmill. In that instance, they revved the RC motor and then set the treadmill speed to exactly match the RC car speed. That's what the thought project is telling you. Where MythBusters went wrong with that preliminary experiment is that they kept the treadmill at a single, static speed while they varied the speed of the RC car. That's not what the thought project explicitly describes. No matter how complex people want to make it or how big a force people want to apply, all that matters is that the rolling speed of the wheel set is expressly described as being matched exactly by the conveyor. We don't have any flexility in trying to change that parameter for this though project. What it's trying to show, again, is that force alone does not result in lift if there is no airflow over the aircraft. You can do a variation of this same though project in a non-controversial way. Take a landing gear set off the aircraft and place it on the conveyor. Give it a shove and you get a certain velocity - call it V1. Guess what speed the conveyor instantly attains. Also V1. Now place the wheel set back onto the aircraft and add whatever force you want so it goes from V1 to V2. The conveyor also matches not only the speed of V2, but the rate of change from V1 to V2. Mathematically, you get the same result taking the derivative of speed to get acceleration or the integral of speed differential to get position. Change in speed is 0; change in acceleration is 0; position is unchanged.

[@Legoless.]

With cars, this conveyer belt would be called a dynamometer. :)

[@unclerojelio6320]

Oh come on man, just when some of us were able to put this train wreck out of our memory you go and dredge it back up again. Have you no conscience?

[@pequalsnpsquared2852]

This whole video is just so damn stupid.

[@grummhd3020]

@@pequalsnpsquared2852 nah, just a case of very unrealistic things coming together

[@eliass.4743]

Which Train Wreck?

[@unclerojelio6320]

@@eliass.4743 This whole “plane on a treadmill” thing dates back to the early 2000’s and was one of the first viral internet events. It spawned many a virulent argument that totally consumed message boards at the time.

[@pequalsnpsquared2852]

@@unclerojelio6320 Wow, people are dumb.

[@jefrhi]

Think of it another way... Replace thrust with a rope. If the rope is reeled in, it doesn't matter how fast the wheels or conveyor are moving, the plane WILL move forward because the mode of locomotion is disconnected from the wheels.

[@Coren999]

There is no rope. All energy of the thrust is converted to belt speed

[@BerndWechner]

@@Coren999 Hilarious mate. The thrust is on the plane and cares not one jot about what the wheels are doing. You didn't even watch Captain Joe at a guess (not that he's right, I address his error in a comment here).

[@donaldfegley6127]

The thrust causes the tires to move faster than the conveyor belt

[@BerndWechner]

@@donaldfegley6127 Nonsense. If you set a constraint on a system that constraint is not broken. The thrust propels the plane forwards. It cares not one jot WTF is happening at the wheels as long as, and this is a limiting issue is considered, any drag they exert that works against the thrust. You have not watched the video clearly nor read my explanatory comment in which I explain how Captain Joe errs, because if you had, you would have a full assessment already of the issue of what happens to the speed of the wheels and conveyor. But the thrust cares not one hour about that unless it causes drag, and propels the plane forwards.

[@wizardoftehtime]

@@BerndWechner So explain this to me then, if the plane moves the throttles forward and the wheels start to move from the ground speed of the plane starting to move, but then the conveyor then perfectly matches the speed of those tires for ground speed, so no the plane in no longer moving forward or backwards, how to the planes wings which have to have airspeed flowing around them to produce lift, produce lift if the plane is not moving at all on the ground so no lift is being produced by the wings? When the engines produce the thrust to get the plane moving on the ground to speed the plane up so the air around the plane is producing lift on the wings, the ground speed is then completely stopped by this conveyor that now puts the planes ground speed to 0 which then means there is no airspeed being produced for the wings to create lift. Just because the engines of a plane done care what happens on the ground does not mean that the wings can produce the lift from having no airspeed to then convert to lift as the plane that is on the ground has to have forwards movement to create the airspeed required for the wings to get the lift needed, but if the forward movement is 0 because the conveyor is now keeping the plane still, which makes the airspeed 0 over the wings, which means 0 lift is now being produced to have the plane take off.

[@razor787]

The way I understand this, is that if the conveyor is matching the groundspeed, the wheels basically double in speed. If the propeller makes the plane begin to move, the conveyor will start as well. So if the plane crawls along slowly at 5km/h, the wheels will do the same 5km, which is matched by the conveyor. But because the wheels spin freely, and the plane is still able to move forward at 5km/h the wheels add on that extra ground speed, and will spin at 10km/h. So matching the groundspeed will simply double the speed of the wheel spin. The test could be done by putting a small model of a plane, attach it to something stationary, then turn the power to full. If you release it, it wouldn't automatically shoot up into the air. It would still need to reach takeoff speed to do it.

[@ClikcerProductions]

The conveyor isn't matching the ground speed, it's matching the wheel speed. If it is matching the wheel speed then ground speed is always 0 and the plane cannot ever take off

[@paldyvik7915]

@@ClikcerProductions Wrong. The wheels can not hold back the plane if the engines are pushing it forwards. Oh, and the wheels are stuck to the plane, right? So they too move forwards relative to the ground. That movement determines how fast the belt is going backwards.

[@ClikcerProductions]

@@paldyvik7915 A force can be applied through free spinning wheels, this is something extremely obvious if you just hold a toy car on a running treadmill, you need to apply a force to keep it in place, if you remove that force the car is pushed backwards through it's free spinning wheels, the same thing can be done with the plane. If you think the plane moves forwards you are either allowing the wheels to slip (which is just super boring) or you do not understand very basic geometry, the only good argument for the plane being able to take off is that the treadmill would reach speeds high enough to produce winds fast enough to reach take off velocity while in place on the conveyor

[@paldyvik7915]

@@ClikcerProductions I'm not stating that there is NO increased force from the conveyor belt moving the opposite direction. What many people don't realize is that these are WHEELS. Wheels are touching the surface below, and normally not slipping much (assuming friction exists). This contact point is however not what determines the speed of the wheel. The speed is measured at the CENTRE of the wheel, which may be moving relatively freely forwards and backwards, disregarding how fast the surface below is moving or not. The wheels are stuck to the plane, and when the engines start pushing the plane forwards, the wheels of course follow. as soon as the plane reaches 1 knot towards the left, the belt has responded and moves at 1 knot to the right. That causes the wheels to ROTATE at an RPM corresponding to 2 knots, but they are MOVING at a speed of 1 knot. The same continues as the plane accelerates and MOVES to the left, and at the moment take off speed has been reached, the belt is going to the right, also at "take off speed". Any argument have seen that the plane will stay stationary are false. Mostly, people assume that the extra rotation induced by the belt are able to magically cancel the push from the engine. Now figure this: 1. Imagine you are in your car, driving at 100 km/h. You probably realize that your wheels are moving at the same speed, right? If not, hand in your license. 2. Imagine a toy car, pointing to the left, with a red string attched to the front. Now pull that string to the left at a constant speed. Do you see the car moving? 3. Imagine the car is standing on a green paper sheet. Pull at that green paper sheet below the car, towards the right and at the same speed as the red string, but in the opposite direction. (You may want to practice with empty hands first, to build confidence in yourself as a researcher.) 4. Repeat step 3, while carefully observing whether or not the car is moving to the left. Repeat one or more iterations until the shock settles. Also observe the rotation of the wheels compared to in step 2. (Hint: The car IS actually moving to the left!) 5. The car is the 747. Pulling on the red string represents the push from the jet engines. Pulling on the green sheet represents the conveyor belt responding to the movement of the plane and its wheels. (Remember step 1?) The fact that the belt moving to the right does not prevent the plane from moving to the left at the exact same speed, as stated in the riddle, proves that the plane will be able to accelerate and its wings gain lift. Riddle solved: Take off OK!

[@ClikcerProductions]

@@paldyvik7915 The speed of the wheels is not the speed of the center of the wheels, that makes it a completely pointless thought experiment, if you want to interpret it that way you can, but that interpretation is so impressively lacking in any level of nuance or intrigue that I would expect a more interesting intellectual conversation from a 5 year old. The wheel speed is very clearly meant to refer to the speed of the surface of the wheel relative to it's center of rotation, I want to be very clear here that YOU are choosing to interpret the though experiment in a way which makes it pathetically dull. Please only reply if you have any interest in discussing the thought experiment the video is actually covering

[@dannywitz]

Myth busters did a great live demo with an actual airplane (ultra light) but still fun to see

[@ricksharpe6895]

And it did take off in case anyone is still wondering.

[@---xv3zf]

@@ricksharpe6895 There's a short 2min clip of that myth here on yt. It should answer your question.

[@MichaelKing4023]

Yes I saw the Mythbusters ep showing a plane taking off on a conveyor belt.

[@gitbse]

Yes, however... he explains this in the second half of the video. The belt they used was meant to match the ground speed of the plane. And ... given the technology... they could not match the wheel speed *instantly and exactly.* The problem is more.with semantics than anything.

[@marsjan]

@@gitbse Yeah, but in that case the answer to the riddle should be that such theoretical conveyor belt would instantly generate friction on the wheels equal to thrust. Only that would prevent the plane from moving. It's a pretty pointless riddle.

[@nirmalaerway7513]

I thought of another way of explaining this: Because the wheels are free-spinning and isolated from the rest of the plane by the ball-bearings in the axle, the spinning of the wheels and the movement of the conveyor belt are effectively a closed system in regards to the forward movement of the airplane. This means that the airplane, ground and air are also a completely separate closed system in regards to the spinning of the wheels and the movement of the conveyor . And like all closed systems, they simply do not affect each other. (The one exception to this is that the wheels do counteract gravity by holding the airplane off of the ground or belt, but this function does not have any impact on the forward movement of the airplane as the wheels and landing gear only apply a vertical force to the airplane body that is counter to gravity.) This all means the plane will take off normally.

[@francescolucakeplero7975]

Bravo Nirmala! Many people, even with good culture, did not understand the trick phrase: "match the speed of the wheels"... it's the key to everything! The plane can stay still, go forward or backward, with the tape on or off... the belt and the wheels in any case and always, "match the speed" The example of the pinion (airplane wheels) and rack (conveyor belt) serves to understand that there is no slippage and "match the speed" in any case and always! The quiz was created to trick ordinary people into comparing a car to a plane, but many of us know that they work differently!

[@MrDefreese]

@@francescolucakeplero7975 the pinion and rack comparison shows that since the two systems are locked as in no slippage occurs, than the speed at the pinion axis is nil. There is no motion of the pinion axis and no airflow.

[@francescolucakeplero7975]

​​@@MrDefreeseYou didn't quite understand the riddle and the trick phrase, the example of a rack and pinion serves to understand both that the wheel and the belt do not slip but especially that the conveyor belt "matches the speed of wheels" in any way and at any time any speed... The gears meet (matched) and copy each other, the pinion (plane wheel) is free to turn and move forward, the rack (belt) can move backwards, the speeds are always "matched" The plane could even move backwards or stand still, the conveyor belt always copies and matches the speed of the wheels... In conclusion, and I don't want to add anything else and I'll stop, the phrase to win is "match the speed of the wheels" It doesn't say that the conveyor belt "matches the speed of plane" As confirmation, we have that the puzzle of the plane on the conveyor belt exists, and there is no such thing as the Ferrari enigma on the conveyor belt because it would make no sense and would prove nothing... The great thing about this plane riddle on tape is that in its simplicity it is brilliant! It works because it leads many to make mistakes, even educated people fall into error which shows that being educated does not necessarily mean being intelligent... In conclusion I would like to say that I would like to compare this riddle to the older one: "the riddle of the sphinx" if after the solution is given that it is man, but there are people who nitpick by making excuses like... You know, however, man is not really an animal... Man doesn't have 4 legs... The stick is not a paw... Sunset is not old age, etc... If you don't have the intelligence to deduce the trick phrase, you will be devoured by the sphinx!

[@MrDefreese]

@@francescolucakeplero7975the speed of the vehicle as measured at the wheel/pinion axis is always zero in the perspective of the environment. See the pinion and rack demonstrations.

[@francescolucakeplero7975]

​​@@MrDefreeseYou still don't understand! I know very well how a fixed pinion and rack works, classic of a steering wheel, but this is not the case! In the case of the airplane on the tape, the pinion axis (represented by the airplane wheel) is not fixed! It is free to both turn and move forward (both forward and backward) and is always matched by the gears You pretend that the airplane works like a car! It's not like that, it means you don't want to understand! Since you have already set an answer, you try to do everything to bring the quiz to a scenario that makes no sense and which would prove nothing, only abstractions! Every now and then you have to try to be more mature and admit that you have made a mistake! The airplane on the conveyor belt riddle is an educational, reality-testable test of logic, intelligence, to prove that the airplane doesn't work like a car! Stop, I don't want to waste any more time on further answers! Don't tag me! Everyone remains in their beliefs!

[@mondariel]

What about BushPlanes? They don’t need runway at all and still can take off. Wheels don’t power plane. Engines do.

[@MrDefreese]

Bush planes definitely need sufficient airflow over the lifting elements and they take advantage of strong headwinds wherever possible. They still have to roll on the ground (and capitalize on clever design) in order to minimize takeoff speed and distance.

[@Bahcorp]

Creating lift by moving the wheels, Genius.

[@grummhd3020]

Magnus effect

[@mitchio83]

Making comments without listening to the video, Genius.

[@danielkochanicek6906]

@@grummhd3020 Plane would spin around wheel axis, since magnus effect is exponential.

[@pcsc1097]

Joe I feel that the answer in the first scenario is absolutely YES the plane would take off! If the plane was a car using its wheels to propel it forward and the conveyer belt could match it no matter what, then it would stand still. An airplane of course uses air to propel itself forward so those wheels would probably be spinning many times their normal rate when the plane is fast enough to fly.

[@debateme9204]

Yeah, I'm not sure is this video is a troll. It makes no sense. It's like the idea of superman using his strength to hold a helicopter down without grabing something on the ground. Strength does not matter, only weight. If the thrust is greater than his weight, he will get lifted.

[@herbaHD]

Actually there is no answer at all because the scenario doesn’t work. If you apply thrust then the plane must move forward but it can’t due to the logic of the problem’s wording.

[@nuk1964]

@@debateme9204 Of course, if we consider that Superman can apparently accelerate in flight to near (or even exceed) the speed of light, there's is apparently some force that is allowing for that (no, no, no! I am *not* going to pursue idea of "jet propulsion" using flatus...). Telekenisis perhaps? Anyway by whatever mechanism that allows for that, he should be able to keep a helicopter from taking off (i.e. he simply uses this force to "push down" to counteract the lift of the rotor).

[@debateme9204]

@@nuk1964 that's my point though. Superman strength is irrelevant in this scenario. He would need to fly otherwise he would just be pulled up into the air. In other words if you take away Superman's ability to fly his super strength would do him no good in this scenario unless he found something on the ground to Anchor himself with.

[@nuk1964]

@@debateme9204 And I was simply pointing out that Superman has abilities aside from super-strength -- i.e. ability to not only fly, but accelerate in flight -- that could be used explain how he could keep a helicopter from taking off.

[@eduardkhachaturyan1189]

Yes it can. Speed of the wheel have nothing to do with airplane speed relative to the ground.

[@mojojojo3852]

But it doesn't matter . What matters is the TAS. And if the aircraft has a GS of 0 it means that there is no wind flow over the wing for them to be effective . So a plane on a conveyor belt would be the same as if it applied full throttle and applIed the brakes it just won't take off .

[@DIBOYOU]

@@mojojojo3852 the engines and only the engines provide the forward thrust, even it was a plane on ski's, on floats, on 'wheels on a conveyor belt', it doesn't matter as long as it does not prevent the aircraft from moving (=attaching it to chains or putting large concrete blocks in front of the wheels - normal chocks won't do the job). If the conveyor belt was moving forward with the same speed, the wheels would not rotate and the aircraft would take of as normal. With the belt running backwards, the wheels will spin twice a fast (only marginally increasing wheel/axle friction) but the aircraft will 'thunder' along the runway thrusted forward by the engines. Maybe the tires will deflate because rotational speed is well above it's max. rating of somewhere around 220+ knots (but that is a different discussion).

[@pik2005]

@@DIBOYOU not really comparable with ski's or floats. If you stop the engines, the plane will go backwards due to friction belt/tire, because the plane has a weight that pushes down on the belt. So a part of thrust will be consumed just to make the plane still compared to ground. You will never be able to reach take off speed, because you'll always have this conveyor speed to compensate. What you say works if the plane weight is equal to zero.

[@DIBOYOU]

@@pik2005 Not true, there is an accident investigation of a DC8 (I think) which had it's wheels frozen and on the slippery runway the aircraft started it's take off movement almost as normal. but given the enormous friction, it failed to take off. In this conveyor example, the wheels will only have minimal increase of friction in it's axles. The take off roll and speed will increase slightly, but as long as the axles don't seize completely due to overspeed, the aircraft will get airborne. If the conveyor belt turns in the other direction, the take off run will be marginally shorter, but the airplane won't lift of like a helicopter even with it's wheel not rotating at all. So yes it is comparable with ski's, floats, etc. all have different gradients of friction, but absolutely far less than the (jet) engine thrust

[@UtopiaTimes]

Lol what about the wind that gives the lift? How high do you fly off the treadmill in the gym?

[@dalibor8806]

ChatGPT: Airplanes take off by accelerating to a speed that provides enough lift from their wings to overcome gravity. The speed of the wheels on the runway is not directly relevant to the plane's ability to take off. If the plane's engines are producing enough thrust to move it forward, and the wings are generating sufficient lift, the plane can take off. In the case of the conveyor belt moving in the opposite direction to the plane's wheels, it won't prevent the plane from taking off. The conveyor belt might make it more challenging for the plane to start rolling, but once the plane's engines provide enough thrust, and the wings generate sufficient lift, it will take off as usual. The key point is that the thrust from the engines and the lift from the wings are what enable an airplane to take off, not the speed of the wheels relative to the ground.

[@tedwalford7615]

Cool!

[@SuperKiller156]

Yes because it doesn't matter what the wheels do on an airplane, airplanes rely on airspeed not groundspeed.

[@AndreasRSD]

No because there is no windspeed. There is groundspeed but the windspeed is none. I don’t know why you said yes because you understand the concept but I assume you already watched the video.

[@LeoH3L1]

@@AndreasRSD Nope, there's nothing the conveyor belt can do to stop the plane moving forwards, all it will do is cause the wheels to be rotating faster than they normally would at the point it takes off. I watched the vid, and I also watched the mythbusters vid, where they actually tested it with a real plane, and it took off with no problem.

[@inisipisTV]

@@AndreasRSD He's playing on the wording of proposition. If there is a strong enough wind that goes on the opposite direction that has enough force to generate lift and the engines can use it push enough thrust, so Yes it can. There are bush planes that can take off with as little 3 feet of ground because of the strong wind in the wildeness. Though the conveyor belt runway is useless and didn't contribute anything to the take-off. As Captain Joe pointed out, the question is tricky.

[@Da-Creams]

Yes groundspeed no wheel speed.

[@cccycling5835]

@@LeoH3L1 They used a small bush plane for that experiment, not a 747. Even a empty 747 will require a certain forward speed or a certain airspeed to generate lift. If the 747 cannot generate enough forward thrust to counteract the trend mill and cannot move forward, it will not take off. I love how people cite myth busters as some sort of gospel. Adam sucks. Long live Jamie.

[@bkm83442]

Another way to think about the problem is to ask, "Can a sea plane take off from a river going upstream?" The obvious answer is yes. The plane doesn't care much about the water speed, only the airspeed.

[@bakkks]

The difference is the river has constant speed while the belt speed is dynamic - it matches the wheel speed. You will not be able to take off from the river IF the river speed matches you forward speed - you will be stationary compared to a tree on the river bank. If the river moves downwards with a speed of e.g. 200 mph - that does not apply to the air at the surface of that river.

[@julese-p278]

@@bakkks The belt could be going twice the speed, it wouldn't matter.

[@svensk69]

Yes it will move forward and take off! But only due to thrust from the engines... The conveyor belt's velocity is completely irrelevant, since the wheels are not powered!

[@tracruz]

How does thrust from the engine allow a plane to take off??? It doesn’t. You need airflow under the wings to create lift.

[@stevenfpv2345]

@@tracruz Yes it does.Thrust from the engine push the plane forward, gaining velocity thus airspeed

[@moebekdache3756]

@@stevenfpv2345 But the plane isn't moving forward at all... The power of the engine is irrelevant, it's not a helicopter

[@stevenfpv2345]

@@moebekdache3756 Yes it is. How does an airplane is supposed to fly once in the air? Once the wheels aren't touching the ground anymore? Engines push the plane forward, regardless what happens to the wheels

[@moebekdache3756]

@@stevenfpv2345 So are you saying, that if 2 forklifts lifted the plane either side by the wing, let engine hit full power, then back the forklifts away, the plane will then go?? Correct me if I'm mistaken

[@Siatkowkarzadzi]

The actual answer and the key to the problem (in first version from the video), which everyone is missing, is: wheels will start skidding (so we achieve forward movement relative to the treadmill and airplane can take off) when the trust exceedes the friction

[@MrDefreese]

There is no real reason for skidding. The whole point of the wheels is for this to be an exercise in rolling wheel behavior.

[@Siatkowkarzadzi]

@@MrDefreese I don't understand what you mean. 2nd Newton's law is as real reason as possible. Wheels will be spinning with the belt matching their rotation speed (teoretically with speed tending to infinity), but the aircraft will start moving forward when thrust > friction, so tires will start skidding on the belt. It's a similiar scenario to a car braking with locked wheels. I know wheels would be spinning in our problem, but the key is the difference in speeds: car's actual speed is bigger than the speed that would correspond to wheel rotation rate. And that's the case in the discussed problem - even if aircratf wheels' rotation speed is not zero, unlike in the car example.

[@MrDefreese]

there is no need for any sliding / friction worries, The only reason the wheels would slide/scrub across the ground is if the bearings are busted and rolling is not the way the wheels would perform. Of course, a meme like this automatically assumes things like perfectly rolling wheels, perfect contact with the patch on the conveyor, instantaneous speed response of this magical conveyor, deformation of the tires is not a factor, etc. Simplifying it to the bare elements, we are dealing with just a vehicle rolling on a conveyor that has the exact matching rolling speed so that the vehicle never advances or 'retreats' no matter what thrust is applied, so there is no airflow involved and thus no lift generated by the airflow over the wings. The trick as mentioned is that the conveyor instantly matches the wheel speed exactly - you need instant response controls and power to run this hypothetical conveyor, but that's the question posed to us. It's what we would see in a physics textbook and nothing remotely resembling a real world situation. @@Siatkowkarzadzi

[@Siatkowkarzadzi]

​@@MrDefreese Well, I assume that we stick to basic physics and that assumptions in the description are constants (if it says that the belt matches wheels speed, then the belt is just capable of it and the wheels will just sustain any speed). Friction is a constant too, because it's the only relevant/significant interaction between the two main objects - belt and aircraft. Without friction the belt has nothing to do with aircraft's movement. I disagree about "textbook" part - in some simple scenario we would consider a car (driven by wheels) as you said, but here we have an aircraft powered by jet engines producing thrust - it's completely different scenario, more complex one - deliberately. So the key to the problem is understanding that not only the lack of relative movement (if we exclude skidding) cannot be neglected, but the thrust force cannot be neglected as well. Physics exercises are often just about basic forces (like friction contradicting some opposite force) or speeds. So my solution satisfies both the laws of physics (in terms of forces) and main assumptions of the problem (matching rotation speeds). We may disagree about assumptions and what parts of reality to consider, but my view on the problem and solution to it is logically/physically valid. In fact, your simplified version (and the explanation in video) just assumes the friction to be infinite, not in any way non-existent.

[@Siatkowkarzadzi]

@csatorna7915 How come? Seems like an assumption you made up. Explain please

[@r_v_t]

I am pretty sure third law of Newton is at play here, eg, the engines push air backwards so the plane must move forward. The speed and direction of the conveyor belt is moot. But perhaps the riddle might indicate the the engines of the plane are not at full trust if you read the riddle in some way?? . At least I would expect full trust in the riddle, wouldn’t you not? Or is perhaps the riddle not complete?

[@ajcoopa]

The bottom line is that the wheels are irrelevant, as the plane isn't driven by the wheels. That's the logical error that people make.

[@bibaso12]

Mythbusters tested it irl. The plane will take off

[@tomaz2007]

@@bibaso12 if the plane takes off then the wheel speed is not matching the conveyor belt speed so you are talking about a different problem than the one in the original question.

[@tomaz2007]

Engines provide a force of thrust which is matched by the rolling friction and air friction of rotating wheels. If a plane move forward you are no longer satisfying the conditions in the question - the wheel and conveyor speeds are not matching.

[@Sirkillsalot22X]

​@@tomaz2007 Which is why that isn't the spirit of the myth, is a deterministically dumb way to argue it because it presents a rule that violates physics to achieve a desired outcome, and is thus about as meaningful as arguing whether or not my imaginary superhero can beat your imaginary supervillain. The original intent of the question was "Can a plane can takeoff on a treadmill going equally as fast in the opposite direction." Mythbusters effectively demonstrated the concept which was bounded within reality. Plane is stationary relative to ground under the treadmill: Plane Vground = 0mph Vtreadmill = 0mph Vwheel = 0mph Plane starts throttling the engine: Plane Vground = 1mph Vtreadmill = -1mph Vwheel = 2mph Plane is now barreling down the runway about to takeoff: Plane Vground = 100mph Vtreadmill = -100mph Vwheel = 200mph

[@Ayelmar]

Of course it can take off! The speed of the wheels' rotation has nothing to do with the plane getting into the air -- that only counts when trying to stop at the end of the flight. The engines are producing thrust which pushes the plane forward, and as long as no brakes are applied, the air moving over the wings as the plane moves forward will begin to generate lift, and once the speed hits V2, you can rotate and start flying, regardless of whet the conveyor is doing under your wheels!

[@Nebbia_affaraccimiei]

exacly

[@Ayelmar]

(After watching) Well, okay, if you want to set up a scenario that requires breaking the laws of physics..... :D

[@zazuch]

​@@Ayelmar It doesn't really break the laws of physics. If the conveyer matched the forward momentum perfectly it would stay still and have zero ground speed and therefor no air moving over the wings to generate lift. Considering IRL conveyers dont move much air even at high speed and the problem itself does not state that the conveyer is also moving the air you have to assume it isnt. IF there was a statement stating that the conveyer does move the air above it then yes the plane would take off. That would be no different then a conveyer pulling a plane through at take off speed.

[@Ayelmar]

@@zazuch Ah, but as noted, you're not driving your wheels against the ground or conveyor below you to move forward in a plane. If it's prop-driven, you're pulling/pushing the aircraft forward against the air surrounding you, not the surface below you, and if it's a jet, you're pulling in air to burn the jet fuel and generating thrust to push the plane forward via Newton's Third Law of Motion ("for every action, there is an equal and opposite reaction"). The "breaking the laws of physics" part comes in because, as Joe stated tbe problem, the conveyor and the wheels would quickly reach infinite speed, breaking the speed of light! But, because the thrust of the engine(s) acts independently on the mass of the aircraft, it will still move forward regardless of what the belt is doing underneath, though the air turbulence generated by the transonic shock waves thrown off by the belt might make the takeoff a *tiny* bit difficult! ;D

[@olican101]

​@@zazuchit breaks the laws of physics because the wheels will match the belt speed + plane acceleration. You can't have a sum feeding off itself without getting infinite, which is impossible.

[@JodyBruchon]

The constraint that the wheel and conveyor speeds must match prevents all forward motion. It doesn't matter if the wheels push or not. Any forward motion will rotate the wheels and the wheels and conveyor must be perfectly locked together. No forward motion = no lift from the wings = never takes off. It's not possible to do this in a real-world scenario because there will always be imperfections that enable forward motion. Mythbusters is wrong. I have a video on the subject that explains in depth. Actually, I have two, because the response to the first one was so full of people not understanding that any forward motion violates the core constraint.

[@firefly4f4]

What happens if the plane is on skids on a normal runway. That actually matches the scenario perfectly, since the skid could be considered a wheel that's not in motion, and the runway an inactive treadmill. The plane is still going to take off because the plane's engine is operating on the air, not the ground. However, the only way I can envision the wheels and conveyor moving at the same speed but opposite direction is if the plane is held stationary relative to the ground as the conveyor moves, assuming perfect transfer of energy from the conveyor to the wheels. Even THEN the plane could still lift off if there's sufficient headwind, as then the plane would be moving relative to the air. This is why you try not to park planes, particularly light ones, in the direction of the prevailing winds.

[@AB-80X]

That's swell Jody. Videos, awesome. Let's hash this out. Genuine PhD physicist here by the way. Okay, GEO physicist, but hey, I do grasp the most elementary ideas of Newtonian physics. I'll start with the opening argument which uses a Boeing 747 as an example. How can the power of four massive turbofan engines who's thrust can roughly be converted to a total of 120000-160000 bhp depending on engine variety, be absorbed by the free spinning wheels? They can't, they are not mechanically linked to said huge turbofan engines. They are mounted on bearings which mechanically disconnect them from the plane and engines. Now your rebuttal and counter argument.

[@JodyBruchon]

@@AB-80X "Genuine PhD physicist here by the way. Okay, GEO physicist" - _Appeal to authority logical fallacy_ "How can the power of four massive turbofan engines...be absorbed by the free spinning wheels?" - _They aren't. The question doesn't say that._ "They can't, they are not mechanically linked to said huge turbofan engines. They are mounted on bearings which mechanically disconnect them from the plane and engines." - _The question imposes a constraint. The engines are irrelevant because they have nothing to do with the constraint. The wheels must not rotate faster than the conveyor belt regardless of being "free-spinning" or "unpowered" or "not mechanically linked" and if there is any forward movement, the wheels are implicitly rotating faster than the belt, so unless you propose the only workaround which is "the plane drags the locked wheels along the completely stopped conveyor belt," the plane cannot take off...not because the plane's engines can't overpower everything holding it back, but because the constraint requires that they don't do that._

[@beauxguss6321]

The aircraft thrust will move the aircraft forward, not turn the wheels to move the aircraft. So, the acft moves forward which causes the wheels to spin. Not even instant acceleration of the treadmill can undo that motion. So the wheels must even momentarily move faster than the treadmill. In this case, the treadmill must now catch up, but it's acceleration will be added to the acceleration of wheels. The forward thrust of the engines, which is not dependent on the wheels will constantly add to the gap until takeoff speed is reached. This is physics. It's like if you put a car on a dyno, but you put the non-drive wheels on it. When you hit the gas, the car will move forward no matter how fast the dyno can spin. That's because the forward thrust is not attached to the dyno. Just like the thrust is not attached to the treadmill through the free spinning wheels.

[@dogboy0912]

You're breaking the premise of the conveyor though. It can do the impossible. Imagine putting an rc car on a Dyno, but then pushing it with your hand (let's say your hand produces way more force than the car or dyno are capable of). In real life, the extra thrust from your hand would push it off the dyno. If this dyno worked like the magic conveyor, the car wouldn't move. You would see and hear the tires and Dyno spin even faster to keep up with the increased thrust proportional to how hard you push. You can pick up the car just fine, but as long as the tires and dyno are in contact, the rule applies and the rest of reality will bend to accommodate. All of your force is instantly counteracted by the dyno because it needs to match the tires, and any relative movement forward or backward would break that rule.

[@beauxguss6321]

@@dogboy0912 ah, but at some point in my pushing, my force would be more than the car weighs and would simply force it off of the dyno. We are not talking about a wall here, just a small surface contact point. If the wheels were the source of the momentum, all this would be true, but because it's an outside force, it will be overcome. Some have mentioned I might be right if the plane "skipped" or slipped. Perhaps that is how it manifests, but the rule of the belt itself cannot be allowed to contravene all other forces. I mean, we already have to throw out breakage and any form of speed limit as a part of the question, but assuming that the conveyor is holding the tires down is a bridge too far for me. The body of the plane wants to move forward, it will.

[@MassRocker]

Even if the conveyor could match the wheel speed instantaneously, it won't produce additional drag. The jet thrust would still push the plane forward and it will take off just fine.

[@fernandoferraz2057]

True. It doesnt mater if the wheels are going 10000 miles per hour backwards.... the plane will move forward...

[@adesignersperspective]

yeah he got this completely wrong. lol. guess that's why he's a pilot and not a physicist. though honestly it doesn't take even that much know-how to realize that a plane is propelled forward by the jet engines and/or propellers moving it through the air - the wheels provide absolutely zero propulsion and are completely irrelevant to the plane's forward momentum.

[@joedagg4495]

But the wheels are acting on the conveyor belt using with the gravity of the plane. If the plane wanted to move forward, the wheels would have to drag against the ground, similar to a plane trying to take off with no wheels.

[@adesignersperspective]

@@joedagg4495 you're doing an impressive amount of mental gymnastics to defend your nonsensical point. no, the plane's wheels don't have to drag against the ground, because the wheels on a plane work like wheels on a wagon - they're not self-propelled. the plane is propelling itself via the jets or the propeller pulling it through the air - EVEN when it's sitting on the ground - the same way is if you are pulling a wagon from its handle, the wheels follow the handle - the wheels themselves have zero role in pushing the wagon forward. you pulling it by the handle is doing that - the same as a plane's jets or propeller are going to pull it forward regardless of whatever the wheels are doing. in the case of the conveyor belt scenario, the wheels are just going to spin against the conveyor belt faster as the plane moves forward at the exact same speed because the wheels aren't offering either resistance nor propulsion - the plane's jet engines or propeller are doing that, and they're not competing with the conveyor belt - they're competing with the air they're pulling through them that's moving the plane forward. the wheels are just like the wheels on a wagon - they'll spin as fast or as slowly as the jets pulling the plane forward require them to, on a conveyor belt or not. something the mythbusters demonstrated quite definitively when they tested this myth. the wheels on a plane ARE NOT moving the plane. the jets pulling it through the air are. so unless you can figure out a way for the air the plane is using to pull itself forward to also move in the opposite direction of the propeller or jet engine's thrust (the opposite direction of the conveyor belt, by the way) at an equal force to the jet engines or the propeller, you're not gonna stop any plane from taking off, conveyor belt or not. the wheels play no role in propulsion - full stop - and are just going to spin faster as the plane moves forward and offer zero resistance otherwise, just like the wheels on a wagon would if you set a wagon on a conveyor belt and stood next to the conveyor to pull the wagon forward with its handle in the air. the wagon would still move forward, even though the wheels would be spinning faster to compensate for the treadmill. same thing with the plane. you're just not making any sense.

[@joedagg4495]

@@adesignersperspective wow you totally don't understand the question do you? I understand the wheels don't generate the force. The issue is whatever Horizontal speed the jets produces, the conveyor belt will match going the opposite direction and since the wheels of the plane act to create zero friction between the plane and the ground, the wheels would literally have to slide against the ground if the plane were to accelerate. Kind of like attaching a horizontal jetpack to your torso, if your legs can't move fast enough they will literally start dragging on the ground. Ever heard of gravity? You can't just throw friction out the window dude.

[@benblakesley5871]

Every time this does its rounds. It turns into a battle between pilots and engineers

[@jphilb]

I hope pilots and engineers are on the same side. I am an engineer and I say it will take off in all cases.

[@marjan8888]

@@jphilb then you are not a good engineer

[@jphilb]

@@joshualengers7743 Put a rocket on the conveyor belt. Bet it will move.

[@quadcopter]

@@joshualengers7743 lift comes from the air passing over the wings. Why do you think the belt should be able to hold back the plane?

[@kestrimurgel5155]

@@joshualengers7743 The wheels are free-wheeling. The plane is effectively on roller skates. If I put you on roller skates and push you forward at 5mph on a conveyor belt, you still move at 5mph but the wheels on your skates move faster than they would normally.

[@MrSupercar55]

It would work. Think about it, airplane engines produce thrust. They don’t drive the wheels on the landing gear as well.

[@MED31MED]

Nope. The plane would explode.

[@chesterwang3070]

How will the wings generate any lift? They won't, so the plane can't fly.

[@Dan007UT]

@@chesterwang3070 I cant believe people still this would work..

[@Schumicomeback2010]

@@Dan007UT sure it can work...if the fan you set in front of it is big enough😂

[@Dan007UT]

@@Schumicomeback2010 haha true! or if its in a hurricane

[@possle]

Its a riddle for a reason In my head, planes use thrust via an engine to move forward so wheel speen is irrelevant l, same way a plane can take off on water

[@NetAndyCz]

I think this depends on the friction between the wheels and the conveyor belt. If the belt was low friction, you can put the park brake on, so the conveyor belt does not move and just take of as if you had skis.

[@bobh6728]

You are 100% correct. When the plane starts to move, the conveyor belt has to move the same speed as wheels, but moving the belt spins the wheels faster. So if there is any friction involving the wheels, the belt and wheels will speed at infinite speed almost instantaneously. The only way to spin them at the same speed is to have the energy from the thrust of the engine be matched by the frictional energy lost by the wheels on the belt. So unless the wheels skid as you say, the given conditions are impossible. Same speed needs to be defined better.

[@Ryan50c]

Not how that works at all, and not the point of the question

[@beauxguss6321]

@@Ryan50c actually, it's a brilliant, out of the box, solution to the problem. The belt doesn't move because the wheels are locked. The engine thrust then pushes the plane forward, belt and all. The only potential drawback is if you say the belt will only move under its own power and opposite the direction of the aircraft. But the principle is pretty hoopy thinking.

[@c1n9r6v3]

▓▒░ I paused this video and thought about it for -an hou- a few minutes. If the conveyor belt is moving in the *opposite* direction at the same speed as the wheels are, this means that the aircraft isn't moving toward the wind. In other words, it's standing still. It would be a miracle if it does take-off. ` Today is Saturday, the sixty-fifth day of the year two thousand and twenty-one. ░▒▓ `

[@Oz_Gnarly_One]

How does a float plane take off against a current? Does the water direction pushing backwards stop you from taking off? The answer is no. Your ability to take off is only governed by the your airspeed. The plane pushes on the air not the water.

[@cm5754]

If the ground is moving, it is possible of course for the plane to move even if the wheels aren’t spinning or are even spinning backwards. The plane can push against the air directly, so it makes no difference which way the wheels are spinning. The only reason the wheels spin is the difference in speed between the axle and the ground beneath them, the freely spinning whee has no significant effect on the speed of the axle or the ground beneath it.

[@rodneyoben4465]

Isn't it amazing to know that no one anywhere in the world has finished watching this video at this time?

[@jakobkindl8704]

Well, Joe has 👀

[@Hydrolegoproductions]

The editor has

[@tylerpierce1861]

The speed of the conveyor will always match the speed of the plane (in the opposite direction) if the conveyor is meant to exactly match the speed of the wheels. He tries to draw a distinction between the hypotheticals “conveyor belt matching the wheel speed” and “conveyor belt matching plane speed” when there is none. As long as the wheels aren’t sliding for some reason (friction/ breaks), they’ll be in contact with the conveyor which means they’d be matching its speed. So, saying the conveyor belt matching the wheel speed is the same as saying it’s matching the plane’s speed. Think about it as the top of the wheels moving it the direction plane is moving (at that speed) and the bottom, in the direction the conveyor is moving (at the conveyors speed). Those speeds added together equal the rotation speed of the wheels. So the conveyor matching the speed of the wheels spinning would mean it’s also matching the speed of the plane. This is how circles works. The only good point here is the mention of the max wheel speed. If the wheels couldn’t spin fast enough (they’d only have to spin twice as fast as they would on a static runway since the runway in this case is moving backwards at the same speed the wheels and plane are moving forward) then yes, that friction would prevent the plane from gaining enough speed to provide lift (air flowing over the wings fast enough).

[@IvanSkyFlight]

Yes, if the movement of the wheels is initiated by thrust, then the plane would take off. The thrust is not related to the wheels. The jet engine is not pushing against the ground. The travel distance before rotation airspeed/Vr would be similar to a normal takeoff. In this scenario the tires would be turning faster but the plane would still be moving forward through the air opposite of the thrust, thus generating lift. The wheels only contribution during takeoff is to mitigate friction between the aircraft and ground. They do not propel the aircraft during takeoff. Maybe this will help: if I hold a non powered toy car on a treadmill with my hand while the treadmill is running I can still make the car move forwards and backwards even if the treadmill were to instantly speed up/slow down as I moved the car forwards/backwards. In this case I am the jet engine and the wheels aren’t the source of power.

[@dogboy0912]

See, it's the qualifier of the conveyor belt exactly matching the speed of the tires with no delay. For this to be true, to take your car example, if I tried pushing the car forward, I would see (and probably hear) the tires and treadmill speed up proportional to how hard I push, but the car would never move forward - that would require the tires to move faster than the conveyor belt. It would be like an invisible, equal, and opposite force, pushing against me. I could even pull on the car until the treadmill and tires are at rest, I could pull even more and make them rotate the other way, but the car would never actually move. To actually move its position relative to the treadmill would be to break the requirements of the scenario with regard to the treadmill. It's not possible, but given the premise of the conveyor, the rest of physics would need to accommodate it. The aircraft will never produce enough thrust, regardless of means, to gain any relative airspeed (or true, or ground, or any motion period for that matter), for it would break the rule of the conveyor. The only way I see a possible takeoff is with headwind equal to or greater than rotational airspeed, or if the engines produced enough of a vertical thrust component to separate the aircraft from the conveyor, or if a hypothetical aircraft is constructed in such a way that the exhaust airflow is sufficient and positioned in a way to impart effectiveness on the control surfaces/wings, which sounds really goofy to me but maybe somebody can tell me if that's even possible or not.

[@IvanSkyFlight]

@@dogboy0912 "It would be like an invisible, EQUAL (emphasis mine), and opposite force ,pushing against me". What force? Why equal? In the toy car example, the wheels would have to overcome a marginal amount of friction as they turn around the axel and where they make contact with the treadmill. Are you suggesting that I could not push the car forward as a treadmill was speeding up, even if instantly? Other than the weight of the car (not even the full weight because of the wheels) and a small amount of friction, what force would I have to overcome? Let's say I push the car forward with 50 pounds of force from my arm which I could easily do. What force is going to push back against me at 50 pounds?

[@HerrinSchadenfreude]

I've heard and seen numerous versions of this question and then also seen a Mythbusters episode on it. How it's asked and how the illustration is presented makes all of the difference in my view. The way it's posed here and was demonstrated on Mythbusters, where the "conveyor belt" is/was a length that at least matched the minimum takeoff distance of the plane, sure the plane can take off. But I've seen this illustrated with a 747-400 sitting on a conveyor belt that was barely the length of the plane. A plane that requires 10,400 feet of runway to take off normally is not taking off while on anything that's barely the length of its body be it a runway or a conveyor belt. If it moved forward at all it would be past that surface within a few seconds of the brakes being let up. The tires and what they're doing or not doing make no difference as I see it for that reason.

[@vossrightfurtwangler9989]

@@dogboy0912 "The aircraft will never produce enough thrust, regardless of means, to gain any relative airspeed (or true, or ground, or any motion period for that matter), for it would break the rule of the conveyor." The engines provide forward thrust. What, in your thinking, prevents the plane from accelerating? If you push the car on the treadmill, what force prevents the car from moving?

[@ThatOneguy-zn6hj]

Its always a good day when Captain Joe uploads

[@thenotflatearth2714]

Of course it can it doesn’t use wheels to provide power

[@97oweb]

Exactly

[@thedausthed]

That does not matter a damn bit! If the belt matches the speed of the wheels then all forward thrust of the plane is being used to not be sent backwards!

[@thenotflatearth2714]

@@thedausthed even if the wheels and the belt are made of sand paper, there’s only so much friction going on between the axels of the wheels and the landing legs which can easily be overpowered by the engines

[@cm5754]

@@thedausthed The belt can transmit a lot of spin to the wheels. But the wheels cannot transmit very much backward force to the airplane, because of their bearings. There will indeed be a slight backwards force due to internal friction, but regardless of the wheel speed the engines will have more than enough power to move the plane forward. If spinning wheels caused huge backwards forces, we also wouldn't be able to coast on roller skates without quickly coming to a stop.

[@davidjvanveen]

Wrong! Think of it this way, if you attach a tow rope to that plane and attach that rope to a vehicle that is not on the treadmill, you can tow that plane off the treadmill no matter how fast that treadmill is going.

[@AWaifuInVR]

You can spin the wheels as fast as you want in any direction you want. The thrust isn't coming from the wheels. I don't know why this is such a difficult riddle.

[@jphilb]

It is not. It looks like about a third of the comments agree that the plane will take of in both cases

[@joshualengers7743]

And that’s the first problem, the second, it wont take off because of the lack of air flowing over the wings.

[@AWaifuInVR]

@@joshualengers7743 Think of it this way, if you put a model car onto a treadmill and you hold it there with your hand you can move it forwards or backwards regardless of how fast the treadmill is going. In this scenario your hand is the air moved by the engines, they will push the aircraft forward regardless of how fast the treadmill is running backwards.

[@sirBrouwer]

it's a riddle where you have to read exactly what the question is. the question is the same as can a stationary aircraft take of when it is stationary? the belt in combination with the engines nullify the other to a 0 point. the engines can put out as much energy backwards (pushing the plain forwards) but the belt is in this case going as fast at the same time going the opposite way with 0,0 time delay. the resulting action in this case means that only the wheels are spinning and noting else. in real life you can't have that. even with a delay of 0,0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.00001 there is enough delay that motion has been made. might it be the belt moving a fraction faster back from the 0 point or the plain moving forward again from the 0 point motion has been made.

[@stephenrowley4171]

@@jphilb it's sad only a third of the comments are right.

[@eeM_Gee]

Plane takes off in both scenarios. Conveyor belt has no effect apart from the wheels friction, but as the wheels spin freely, the aircraft engines would push the plane to proper airspeed and let it take off.

[@Maniacguy2777]

That's what he explained accurately.

[@fyrtiotva]

@@Maniacguy2777 no, he said the first scenario was impossible, it is not.

[@Maniacguy2777]

@@fyrtiotva he said if both in equal speed the conveyor belt and the plane in equal speed is possible to take-off

[@ricardoolivo5244]

not necessarily, the interaction between the belt and the airplane wheels is the key here. If the belt moving back literally and effectively moves the airplane back and thus nullify the engine going forward, then lift off is pretty much impossible for a 747. But, if the belt moving backwards just makes the wheels spin faster, then sure, the plane will move forward and eventually fly. That is the key.

[@themusicalpotato3297]

No, there won’t be any lift.

[@avikahn7403]

yup the exact answer (I hope) as there wont be any airflow which should create lift.....technically if you push the plane strong enough it could take of without any engines (just confirm that for me Captain Joe)

[@thecomedypilot5894]

Easiest answer ever... the wind needs to hit the aileron at a certain speed, and if the plane is literally standing still, it won't do that. That's literally no different than a plane sitting at the gate, will it just take off like a helicopter? No, it won't.

[@ottodepotto5956]

I think it wil be able to take of of the conver belt is fast enouf. There will be enouf air going over the wings

[@thecomedypilot5894]

@@ottodepotto5956 No, it's the opposite. If the conveyer belt is moving at the same speed as the plane's wheels, then the plane is essentially stationary with no wind hitting the wings and ailerons, therefore it won't produce and lift as the plane's real ground speed is 0.

[@SterlingRalph]

@@thecomedypilot5894 plane is NOT stationary though! It doesn't matter how fast the wheels are moving underneath - if the plane is pushing against air then it'll move forward no matter what! Planes don't use wheels for power, so it's completely different from a car!

[@onedaya_martian1238]

Here is a trick. Imagine the plane has a hovercraft base. It is lofted above the ground by a cushion of air. Can it take off ? Of course it can ! The plane is moved forward by the the forward reaction of the plane to the movement of air moving backwards. As a result of this forward motion, surrounding air moves past the wings, such that, because of the curvature of the wings, there is less pressure above the wing than below. This results in lift and the plane rises. This means that, regardless of what is happening under the aircraft...wheels, opposite magnetic fields, a cushion of air, a conveyor belt...the plane will move forward and fly when it has enough lift provided by the wings. If one wanted to watch a plane "levitate" i.e. appear to fly vertically without upward thrust, one could use the same undercarriages as above, but provide a fan or other wind generator to move air past the wings, and use a propulsion device (prop/jet) to provide an equal and opposite force to wind, pushing or pulling the aircraft. Hopefully this description provides enough abstract elements for the imagination to conceptualize how this worked. The video editing of the execution of this experiment did not really show that the plane still moved forward sufficiently to provide lift and fly... while, at the same time, the "conveyor belt" was simply spinning the wheels underneath as they simply held the plane up as it moved.

[@gabriel7932]

But it isn’t; there is a mechanical connection between the wheels and the plane, and the wheels are practically connected to the ground. Unless the wheels slip there is no motion

[@Pappadumful]

3:28 No, the wheels/conveyor would not reach infinite velocity. It would reach equilibrium where the max engine power would equal the power required to overcome rotational drag of the wheels. Granted, they would be spinning mighty fast, but not infinitely fast.

[@sizone]

exactly! LISA IN THIS HOUSE WE OBEY THE LAWS OF THERMODYNAMICS!

[@jnmwtkns]

Dose it say if te engines are up and running at take off power? Im sorry i didnt watch the video its not a complete scenario.

[@ChristopherBurtraw]

True. But since we are accounting for these sorts of externalities, my response is that the belt, tires, bearings, etc would catastrophically fail long before the engines are maxed out by drag.

[@louisrovegno542]

If the plane is moving forward in scenario one, it means the wheels are moving faster than the conveyor belt. This violates the premise of the question so it’s impossible. It’s a silly hypothetical and scenario 2 is way better. But people often misstate the riddle as scenario 1 and then get mad when people insist takeoff is impossible.

[@denoredo]

Imagine a toy plane on a treadmill and a hand which acts like the plane engines pushing the plane forward. Would it get enough air speed or any at all for takeoff?

[@wl6558]

This guy gets it. Perfect explanation. Definitely no significant hurdle for the omnipotent hand (engines)

[@donsample1002]

Mythbusters did this one, starting with small model planes, and working their way up to an actual piloted small plane: kzbin.info/www/bejne/j4C1dJ5nd7Nqh7s

[@debateme9204]

If your hand reaches take off speed, the plane WILL in fact take off

[@toasterhavingabath6980]

@@debateme9204 I mean, if you don't move forwards, you cant make lift

[@debateme9204]

@@toasterhavingabath6980 If your hand is moving at take off speed....that means you are moving the plane forward.

[@LeoH3L1]

The only way this doesn't take off is if the plane and the conveyor belt are in a vacuum chamber.

[@limitedkanji]

Lift?

[@jasonlee3247]

@@limitedkanji no, I’ll use the stairs thanks

[@limitedkanji]

@@jasonlee3247 lol

[@guessmyhandle]

If it doesn’t have air, how do the tires move?

[@LeoH3L1]

@@guessmyhandle Read my post again, CAREFULLY.

[@alexsmba]

It’s always the “matches exactly the same speed” that gets people. It wouldn’t take off because the plane would be stationary relative to the ground and wind. Unless there is a 200 knot constant headwind. lol

[@jagheterbanan]

Nope the speed of the wheels and conveyor belt has no influence on whether the plane can takeoff or not. Plus as soon as the plane starts moving it’s physically impossible for the belt to go the same speed as the wheels.

[@alexsmba]

@@jagheterbanan that’s pretty much what I said dude. It wouldn’t take off WHEN THEY ARE AT THE SAME SPEED. I didn’t say the plane wouldn’t be able to get itself out of that situation.

[@fredericosilvadias4218]

I still think that this explanation is wrong. The plane will move throught the air. The wheels just spin at both speeds (air + conveyor belt) and the will move until is plane airspeed and lift

[@MrDefreese]

@@fredericosilvadias4218 I the vehicle is on the ground. It has to roll.

[@topfelya]

I love when you say it in German 5:44

[@jimday666]

Because he's German...

[@treeinafield5022]

@@jimday666 what's with the "..." ?

[@jimday666]

@@treeinafield5022 *sigh*. He's German

[@man_on_wheelz]

My answer before watching the video: yes, it can still take off, regardless of the speed of the wheels that engine is pulling on the surrounding air and those wheel bearing will probably give way and break the wheels off and the plane will still proceed forward with no wheels (theoretically)

[@sizone]

we werent given that info. remember this is a magic conveyor which can move at infinite speed, so i assume these magic wheels can survive magically high speeds without failing.

[@jnmwtkns]

@@sizone yea terrible question forming. Trick question. Plane needs to generate lift first and foremost before any magic can happen.

[@craiggamache2211]

@@sizone Then the wheels are getting dragged off the conveyor because regardless of what the wheels are doing, that plane is moving forward.

[@JMcKey21]

Wheel speed matters not one bit. Ever wonder why you’d want to put your small prop plane inside if there’s a windstorm?

[@RoundeyeSamurai]

the wheels and treadmill are a red herring in this scenario, it doesn't affect the thrust produced by the engines which determine the airflow and thus lift. That is why Air Speed is important in flight, and not ground speed

[@ClikcerProductions]

You are just wrong. No one is saying the conveyor belt affects the thrust produced, but the basic geometric fact at the centre of this issue is that if the contact patch of the wheel is moving backwards at exactly the wheel speed then the net velocity of the wheel MUST be 0, literally just google "velocities on a wheel". You'll see that in every single case where the bottom of the wheel is moving backwards at the wheel speed that the centre of rotation has a velocity of 0. 0 velocity means no air speed beyond that of the wind, and wind isn't gonna make a 747 take off

[@luketimothy]

@@ClikcerProductions good thing the velocity of the wheel has nothing to do with the forward velocity of the aircraft. The plane would take off.

[@szilveszterszalai230]

@@ClikcerProductions starting by “you are just wrong” and then being wrong is a whole new level.

[@ClikcerProductions]

@@szilveszterszalai230 if the wheel speed and treadmill speed ate identical literally by definition the plane can't be moving forward, if the plane is going forward then wheel speed is exceeding treadmill speed and you've completely ignored the question, set up your own different question, and claimed the correct answer to the original question is wrong 🤦‍♂️ that is the level of stupidity you are at, someone said 2+2=4 and your answer was "nO oNe PlUs OnE iS tWo"

[@drabberfrog]

You completely misunderstand, the wheels definitely do matter. If they didn't then breaks wouldn't work to slow the aircraft down. With the runway spinning faster and faster to match the speed of the wheels and with no slipping the aircraft isn't going anywhere.

[@TheAlfsterino]

Mythbusters did it. Newton's Third Law is the important thing. The conveyor belt is exerting a force on the wheels not the plane. The engines are exerting a force on the plane not the wheels hence the plane moves forwards and thus gets the air across its wings to give it the lift.

[@myflight448]

Myth busters experiment was flawed - If you watch carefully the aircraft does move forward on their conveyor belt , therefor generating lift over the wing, also remember they used a single engine propeller aircraft so the propeller was providing airflow over the wing and the elevator giving them some control authority to rotate all this combined with the forward movement that is what caused it to fly. and aircraft like a jet that is not creating any airflow over the control surfaces or wings.

[@70baja]

@@myflight448 yes, the plane did move forward on the conveyer. That's the point. The relationship between the conveyer and the wheels have nothing to do with the thrust generated by the engines

[@myflight448]

@@70baja Yes the key point here is they had airflow over the wings a) from the propeller and B) from the the fact that it moved forward nothing to do with the conveyer belt- where as with a jet like in the video above there is no airflow so it wont get airborne - This is fairly simple understanding of Principle's of flight

[@70baja]

@@myflight448 why wouldn't there be airflow? The engine thrust will move the plane forward no matter how fast the wheels are spinning. Imagine a child holding a toy plane against a moving exercise treadmill. The child can overcome any slight resistance from the wheels by simply moving the plane against the direction of the treadmill. That's what the engines are doing in this scenario

[@70baja]

@@myflight448 also, are you saying that prop airflow provides lift? That would mean that a pusher won't fly. But they do. It would also mean that Wile E. Coyote's sailboard with a fan mounted on the back would actually work. But it doesn't

[@jthj]

There isn’t enough friction in the wheel bearings to overcome the thrust and thus stop the plane from moving. It also won’t reach infinite speed. The plane will take off with the wheels spinning 2x takeoff speed. Once that happens the conveyor wheel speed escalation stops since there isn’t enough friction between the wheel and the conveyor.

[@sizone]

yes there is, because the magical theoretical question designs it to be exactly that -- the wheels move faster and faster (without failing, cuz they're magic) until the rolling resistance produces sufficient friction and energy dissipation until it equals to the engine output energy

[@ClikcerProductions]

If you're saying that their isn't sufficient fiction you're reading that "the conveyor belt is designed to exactly match the speed of the wheels" and just saying "nah" in response. This isn't a physical scenario, it's a thought experiment, and the simple fact is if you say the plane moves forward you have completely ignored it

[@beauxguss6321]

@@ClikcerProductions even in this scenario the plane will move forward. It must do so for the wheels to turn at all. So for whatever length of time it is, no matter how short (say 0.0000001 seconds) the plane must move. That means it is faster than the conveyor. When the conveyor instantly matches that speed, it only adds to the wheels speed, playing a never ending game of catch up. Additionally, the engine thrust will continue to add to the gap between the conveyor and the wheel speeds up again, ultimately reaching take off velocity.

[@ClikcerProductions]

@@beauxguss6321 If the plane ever moves forward you have ignored the thought experiment entirely, it's that simple, I'm not going to argue because that is literally just a basic fact of the extremely simple Geometry of the problem

[@beauxguss6321]

@@ClikcerProductions if the plane doesn't move forward you have ignored the physics involved. Let's take this off of the runway and put it in the gym. Get on the same speed matching treadmill wearing roller skates. You can't move forward by skating, since the treadmill will match the speed of your wheels. But if you reach out and pull yourself forward using the frame of the treadmill (or a friend on the ground pushes you forward) no amount of speed matching will stop you from moving forward. This is because there is a force outside of the relationship between the wheels and treadmill that is providing the momentum. When the treadmill tries to match, it merely adds that extra speed to the free spinning wheels. It's the same for the plane.

[@nirmalaerway7513]

There is one more problem with the idea that the plane would not move forward: It violates Newton's third law of motion that states that every action has an equal and opposite reaction. When the jets are exhausting their gases out the back of the engines, the equal and opposite action to that 60,000 pounds of force moving backwards is the forward acceleration of the airplane up to airspeed and beyond. No matter what the belt is doing, a motorized belt and free spinning wheels are incapable of creating an equal and opposite action/force of 60,000 pounds of thrust to counter the action of the engines. In addition, if the plane truly is stationary relative to the ground, then there is no motion of the wheels or the belt, as the wheels have no motor and the belt simply matches the speed of the wheels, which would remain stationary as long as the plane was stationary. A stationary belt and unmoving wheels are especially incapable of creating an equal and opposite force/action to 60,000 pounds of thrusting exhaust gases. And even if you run the belt at very high speed in the opposite direction to match a hypothetical speed of the wheels if the plane was moving, almost none of that movement of the belt is translated into force applied to the airplane. And finally even if it was somehow translated into force opposing the jets, it would still not be enough force to counter the jets and stop the plane. I am afraid that Newton's laws of motion in this case trump any hypothetical realm where the plane remains stationary. Bottom line is that the only thing that is capable of countering the thrust of the jet's exhaust and thereby obeying the laws of physics is forward motion of the airplane....and a lot of it!! PS: I am not sure I want to fly with a pilot that does not understand the laws of physics 😛

[@TheOtherNeutrino]

The problem I see is people’s understanding of the conveyor matching wheel speed. If wheels aren’t skidding, then the conveyor is already matching the wheel speed regardless of what the plane above is doing or where the wheels are relative to everything else. They’ll act like two fully meshed gears and the plane still takes off because it doesn’t affect the rest of the plane.

[@BerndWechner]

A genius perspective on the problem, and I tip my hat to you.

[@Knewman7777]

For the plane to move forward through the air and on the belt, the wheels' circumference would have to cover a farther distance than the belt traveled when comparing each to the stationary ground. Otherwise it would be just like you said with the great gear meshing analogy. That's why the question is flawed. There's no situation where this would happen in real life, because the belt and tire accelerating to infinity as soon as the engine thrust is stronger than the friction in bearings and between wheels and runway.

[@BerndWechner]

@@Knewman7777On what basis is this specious claim made: For the plane to move forward through the air and on the belt, the wheels' circumference would have to cover a farther distance than the belt travelled when comparing each to the stationary ground. Again, did you even watch those video? There is zero reason to say that, none, zip. It is a constraint of the problem that the conveyor matches the speed of the wheels, there's not "but ...", and it is a physically inescapable reality that thrust does not care one jot about what the wheels or conveyor are doing beyond any drag they create. Done. Finished. No influence. Thrust pushes the plane forward and the wheels do what they want. If you read my response to Captain Joe (which you seemingly have not done either) he makes the mistake of concluding that the impulse response of the conveyor is immediate, that it is instantly always they same speed as the wheels, and the control system has infinite information transfer (so the little wheel rotation sensor that sends an RF signal to the conveyor motor achieves the impossible of infinite speed) and then he concludes, in this scenario that the wheels and conveyor would accelerate to infinite speed the moment the thrust pushed the plane and his conclusion is that because infinite sped is impossible the plane would not move. And my response is, if he assumes infinite speed of the signal consistency demands infinite speed of the wheels is also permitted so no problem and the plane takes off. If however you drop this silly assumption of infinitely fast response and it has a finite response. then perforce, how fast the wheels and belt accelerate in their tight coupling is a function of the response time. Either way, they will accelerate at a finite rate and reach a finite speed by the time the plane reaches take off speed and again no problem. If however you accept that the wheels and belt have a speed limit beyond which they functionally disintegrate and the plane comes to a skidding halt on the runway, then whether you reach that speed is a function entirely of the ratio of the belts response time and the acceleration of the plane (due to thrust).

[@psychosis7325]

Wheel speed does not matter unless rolling resistance is greater than thrust of engines so it should take off.

[@MrDefreese]

The speed of the vehicle is only due to rolling. The explicit constraint of this exercise is that rolling speed is exactly neutralized by the magical adaptive nature of the conveyor. That’s why he gave the follow-up example if the conveyor had a steady speed which could be overcome by an acceleration (thrust or increase automobile speed). He explained it correctly.

[@psychosis7325]

@@MrDefreese That's my prediction not a counter, also if rolling resistance is greater than the thrust the wheels don't turn, the conveyor would thus be still and plane goes nowhere. Its like trying to take off with the park brake on.

[@Jashtvorak]

@@MrDefreesethe speed of the vehicle is not due to rolling of wheels. The thrust of engines is pushing the plane forward. How would the belt create a counterforce to that if wheels are rolling freely?

[@MrDefreese]

@@psychosis7325 not correct. The wheels just roll along on the surface. The wheels don’t seize in place. He shows this in his first animation of the scenario.

[@MrDefreese]

@@Jashtvorak the vehicle only moves forward by rolling on the surface. You are given the express condition that the surface is moving at the same speed as the wheel which is exactly the vehicle speed. They are one and the same. For extra thought projects, we could resolve the force involved for such a conveyor. It is obviously impractical and out of the bounds of normal engineering design.

[@frankietrancewarrior]

A video on a start up from cold and dark would be super interesting

[@archieapa]

I disagree on your first answer that it will not move forward and take off. Ideal scenario: the free wheel should be considered as a roller with no friction. If you draw the free body diagram, the only force acting on the body is going down which is force due to weight. Even if the ground is moving in whatever direction in whatever speed in whatever moment in time, the body should stay stationary with respect to its initial location in space. Non ideal scenario (except that the impossible conveyor belt exist): The friction on the wheels (rolling friction, mechanical efficiencies, etc.) will create a force opposite to the force of the direction of the thrust. However with enough thrust, it will overcome the force due to friction, thus induce a motion forward - w.r.t. its initial location in space and according to the direction of thrust - and generate lift.

[@mufasah342]

No airspeed = no takeoff. Edit: I realized later that I was wrong and understood the problem with a skateboard on a treadmill. The planes propulsion is through the jet engine, the wheels are free spinning and will only affect the plane if the brakes are activated.

[@sbosboniso7036]

The conveyor belt’s speed only affects the wheels, which are free-spinning.The jet engines push the plane forward through the air.Therefore, the plane will still move forward, generate airflow over the wings, and take off.So, even on a treadmill, the plane will take off because the engines move the plane forward relative to the air, not just relative to the treadmill.

[@sebsshenanigans]

​@@sbosboniso7036but then if the plane does move forward then that means the wheels are spinning faster than the treadmill. It specifically says, treadmill matches wheel speed.... cancelling out the possibility of being able to roll forward

[@calebfuller4713]

@@sebsshenanigans The wheels have NOTHING to do with the force moving the plane forward.

[@sebsshenanigans]

@@calebfuller4713 but if the plane moves forward on the belt... then the wheels are spinning faster than the belt aren't they? Which it specifically states that they spin at exactly the same speed

[@calebfuller4713]

@@sebsshenanigans Yet the plane must move forward, in accordance with Newton's 3rd law. The force of the engine thrust MUST act to push the plane forward. Any other result breaks basic physics. That plane IS moving forward, regardless of what is going on with the wheels. So if you take that interpretation - a belt that always and instantly increases in speed to match the wheel, you end up with the engineering impossibility of a conveyor belt that MUST spin at potentially infinite speeds.

[@Ogspotlite]

To the one person reading this: you’re a legend and adorable, stay safe

[@Banmuyuan]

at kzbin.info/www/bejne/j2eXi5eJlqmXpdE the wheel spins at TWICE the speed of the belt - breaks the condition of matching speed. Captain Joe, you are wrong.

[@BIGTAZ351]

You are "assuming" wheel speed is based upon its "RPM" which fails physics. Wheel speed is its relative movement to the medium. Ergo if the aeroplane is stationary, and it's wheels and conveyor are spinning, THAT breaks the rules of the question.

[@yaczone]

You can’t claim an imaginary runway and also not give me an equal set of imaginary strong wheels that won’t explode. The question sets the stage for me to assume some liberties as well. The plane takes off.

[@jacobkraus7279]

no, because the plane needs air traveling over the wing to create lift, the wheel speed doesn't matter

[@nascardrawings7700]

The time-lapse at 5:50 is really cool. I didn't know the body of the plane rises as it increases speed on the takeoff roll, I thought the body stayed at the same ride height until the pilot rotated.

[@simonbrunner3062]

The wings are designed to create lift even at zero angle of attack. Not enough to make the plane lift off at reasonable speeds, but enough to reduce the load on the suspension. Just like a racing car gets progressively pushed to the ground with increasing speeds due to aerodynamic downforce.

[@tedwalford7615]

It depends on the pilot's settings of the control surfaces. These can be set to hold a plane onto the runway past the point it had sufficient lift, or caused to lift the plane prior to when it could sustain flight (terrible idea), or to balance the forces such that the plane will itself lift at V1 or some other desired speed.

[@bcreason]

Yes but a little slower unless the tires explode due to centrifugal force. There will be slightly more friction in the wheel hubs as the wheels will be spinning twice as fast. There would also be some energy loss from inertia due to having the tires rotation brought up to double the speed.

[@codyj9983]

Centrifugal force isnt a real force. soooo...

[@sigmaoctantis_nz]

@@codyj9983 Soooo that doesn't stop wheels from ripping themselves to pieces if they are spun up too fast.

[@codyj9983]

@@sigmaoctantis_nz but that won't happen...? Why does anyone think a tire could spin so fast that it rips itself apart? The plane will take off before that even comes close to happening.... Understand that a propeller plane flies because the propeller pushes air past the wings to cause lift and so the plane can be stationary (by putting it on a conveyor belt) so long as a propeller is blowing air over the wings the plane will take off. This does not work with a jet engine. And literally has NOTHING to do with the wheels. Drive a plane forward at 100mph with a conveyor belt going the opposite way at 100mph so the plane doesn't move it will still take off because it's the propeller that is pushing the air past the wings, not the speed at which the plane is moving forward. It's the propeller!!!!

[@craiggamache2211]

Scenario 1 just doesn't make sense. The plane is going to move forward from the thrust of the engine regardless of what the wheels are doing. If the wheels and the conveyer were moving at the exact same speed then the wheel would be dragged off the conveyor when the plane gets pulled forward.

[@charlieryan6550]

Joe, it is the wind over the wings. If the that determines lift...wheels have nothing to do with flying. I think your 2nd answer is nonsense.

[@faizanjanjua5397]

Was just going to say this. I was a little disappointed in his erroneous answer

[@stever4899]

I agree.

[@KillarneyMark]

Sorry. Joe is right and you are wrong. But his diagram is not clear and so I can see the confusion. In the first example the conveyor is matching the engine thrust, so the aircraft will always be stationary and because - as you say - it is airflow that counts, the plane will not take off. But! In the second example the conveyor does not match the aircraft power. It is set to a fixed speed. So once the engine is pushing harder than the conveyor, the aircraft will start to accelerate along the conveyor, gaining airflow and taking off. Joe’s diagram is silly because it shows a short conveyor. The real conveyor would need to be as long as the real runway! But the real point is that a car puts power down through the wheels. To move faster than a conveyor you have to first push the engine to match its speed, and then push it even harder. But an aircraft doesn’t put its power through the wheels. So once you have matched the conveyor speed, you would just accelerate normally, with normal engine power. ie if a car’s top speed were 200mph, and you put it in a conveyor going 100mph in the opposite direction, the car would be able to go no faster than 100mph compared to the ground. But if an aircraft’s top speed were 200mph, it would be able to reach that. The conveyor is backwards momentum but it can be overcome.

[@Gooliverr]

I'm still pretty sure that in the first case if you neglect any friction, gyroscopic effect and accept that the wheel and treadmill will accelerate to infinity, then the thrust will still push the plane forward

[@billrobertson5895]

For the plane to move forward the wheels would have to move faster than the treadmill but if there was no friction the wheels could be locked and skid down the runway to take off velocity

[@Ryan50c]

No.. if the treadmill goes in the opposite direction perfectly matching the plane's acceleration, the plane would never move at all.

[@Gooliverr]

@@Ryan50c Dude, basic dynamics - if the wheel's internal friction and conveyor belt's acceleration matches plane's thrust coming from the engine, the plane is not going to budge. But if we neglect internal friction or have a delay with matching conveyor belt speed, then bit by bit the plane will start moving forward and eventually take off. Hence this problem has no answer because of lack of information

[@Ryan50c]

@@Gooliverr "basic dynamics" but ignoring the basic points of the question. No one cares about the friction to the belt or internal wheel friction. You're missing the mark. It's a hypothetical question. The plane stays at the same point in space, doesn't generate lift.

[@Gooliverr]

@@Ryan50c So you just answered the question yourself - neglecting friction = conveyor belt has absolutely no effect on the forces vector that influence the plane movement. The plane by deduction won't stay in the same place since there's no force opposing engine's thrust, hence the plane will move forward, even if the conveyor belt's acceleration is infinitely big

[@shrirangpatil007]

Could you please make a video on different engines of aircraft, i.e, turboprop, turbofan, jet engines, etc, and what are their specific purposes, advantages, and disadvantages? Also why some planes still prefer to use propellers instead of jet engines which are most prevalent these days? Also, can you shed a light on the history of the development of aircraft engines?

[@CaptoCapri]

This topic is hands down the best way to discover if a person is intelligent or ignorant. Ignorant people will say it can NOT take off, intelligent people KNOW without a doubt that it WILL. I'm not wasting my time to even attempt to explain because you were simply born with the mental capacity to understand this, or you weren't. Just know if you don't agree with me, you are suffering from the Dunning Kruger Effect... Google what that is if you're not familiar.

[@nelsonmarques1334]

A plane can take off without wheels, so I think they are pretty irrelevant if they are on a conveyor or not.

[@AtharvaSathaye]

🤣I am curious about your statement...how will a plane take off without wheels plz elaborate!

[@nelsonmarques1334]

@@AtharvaSathaye Seaplane

[@rdspam]

“The airplane has to move forward relative to the ground”. Do you think that you had a headwind equal to Vr you couldn’t take off? That ground speed, rather than TAS or IAS is what governs flight dynamics? Really? If the engine is generating thrust, Newton tells us the plane moves forward. If not, where is the equal and opposite reaction? All the conveyor belt is doing is spinning the wheels up at double speed. I am confounded that this experiment has been done and it was proven the plane takes off, but some people ignore experimental evidence because it conflicts with their (faulty) understanding.

[@michaloravec6431]

Discaimer: I understand in practice (speed of belt = ground speed of plane, or any other higher reasonable speed the wheels can handle) the plane would take off no problems since the engines of a plane are not dependent on the wheel speed. The main issue in this ridle is as you wrote: "All the conveyor belt is doing is spinning the wheels up at double speed." Since the ridle says that belt matches the speed of the wheeels exactly it is now mooving at double speed also. So the wheels are moving at triple speed now. Belt matches and wheels are at 4x speed. Belt matches and so on. This has only 2 solutions: Wheel Speed = 0 - plane not moving so it does not take of. Wheel Speed = infinity - Wheels explode, plane on fire due to friction, black hole forms when speed reaches speed of light, either way plane propably not taking off... The riddle as witten just messes with math a little. From physics we know speedOFwheels = speedOFbelt + airplanegroundspeed. But since the ridle says speedOFbelt = speedOFwheels that is only possible if airplanegroundspeed = 0.

[@jefrhi]

I'm with you! I'm embarrassed to admit that I, incorrectly, thought the plane wouldn't be able to takeoff when the Mythbusters conducted their test. I'm a lifelong aviation enthusiast and huge fan of Capt. Joe but disappointed that he got this wrong.

[@loloverlord1664]

Someone shared that on 9gag, and that was my explaination: - A plane is lifted by an airflow above and (most importantly) under the wings. - That plane on the imaginary conveyor belt is simply immobile relatively to the air surrounding wings. It doesn't matter how you twist it: turning the engines on, buying 24 elephants to pull the plane with ropes, pouring nitro into the engines... It's irrelevant: every thrust you can generate is nullified by the conveyor belt. So relatively to the air, it's an immobile plane. - You don't have an airflow under your wings. - The plane cannot possibly take off.

[@MrDefreese]

Correct. The change in speed is always zero because of the adaptive conveyor behavior.

[@Siatkowkarzadzi]

This is true ONLY as long as pulling/pushing force is less or equal to the friction between the wheels and the belt. In our case if thrust will exceed the friction, the aircraft will start moving (tires will start slipping/skidding on the belt)

[@A38]

This is true. The best way to explain the phenomenon is that you're just trying to get the engines going fast enough, that's it. Once the engines are at full speed, you achieve lift, whether or not your wheels are spinning. You can't just spin your engines up to full speed while you're sitting still though, that's why it's crucial that the treadmill be able to accelerate and match the speed of the plane. If the treadmill was stuck below some speed which would accommodate the engines reaching sufficient power for lift, there'd be no lift.

[@MrDefreese]

@@A38 you only achieve lift by having airflow and in this case, the vehicle motion is in equilibrium with this stupid conveyor. The resulting speed of vehicle is nil…while it is on the ground trying to roll. Another way to simplify this even more is this - remove the wheels; make it a big block with a force applied to it while on a conveyor. We know the formula for pushing a block with sliding using kinetic friction coefficient. That gives us acceleration/velocity, We know this stupid conveyor is designed to exactly match that speed. It’s doable, but it’s a stupid textbook problem.

[@ivani3237]

@@Siatkowkarzadzi No, force of the belt is multiplying to lubricated bearings in the wheel friction, which is for theoretical experiment is equal to zero !! So backward force is zero, forward force - regular force from propeller

[@savvasafantenos5951]

Capten sorry but your plane will lift off in any case. Matching or even double the speed of the belt backwards it (if the weels can hold the spin) you will take off! If your consider is about if the weels can hold on the frictions ect it is another riddle

[@MichalDabski]

The conveyor belt has no means to stop the airplane from taking off since there is no friction. The plane uses only air to push itself forward so it doesn't matter in what direction the ground moves. All that matters is air speed and if it'd high enough, the plane can take off even from stationary position.

[@stephenhalby]

An MTOW 747 has a LOT of friction just taxiing and taking off under normal circumstances… it won’t even move at all at only 26% N1 under normal circumstances at that weight. If there was no friction, it would easily move at 26%…

[@julese-p278]

@@stephenhalby You are mistaking inertia for friction. It takes 26% to overcome the inertia, you can throttle back a lot more after that and the engines will propel it forwards. You claim to be a pilot, try it, you'll see. You're just wrong. And it is truly scary that you fly anything bigger than a Cessna, if in fact you do.

[@clashingimages]

It’s simple physics. The answer is in the riddle itself. Wheel speed the same as the belt. A plane will NEVER take off with that variable. It will ONLY take off if the wheel speed is greater than the belt (aka forward thrust pushing it along) It’s a question that gives you the answer by giving you an illogical physics problem

[@MrDefreese]

Exactly. It tells us right from the beginning.

[@SproutyPottedPlant]

Nah it'll probably fall off the end as the wheels overspend and explode!

[@MJSmithGroup]

No. There wouldn't be infinite wheel spin speed. If the engines are providing thrust, the airplane is going to move forward (relative to the air and/or ground) commensurate with thrust as per normal regardless of how fast the conveyor is going or how fast the the wheels are spinning. But even at that, the wheels & conveyor max out at ~2X the actual speed of the plane as it moves forward through the air (and relative the actual ground).

[@NikolausUndRupprecht]

1:00 Take-off shouldn't be a problem: Planes gain speed by generating thrust with the engines mounted to their wings. Are there even any motors rotating the wheels? I don't think so. 🤔

[@DIBOYOU]

No motors in aircraft wheels (except some experiments with 'electric taxiing') that are assisting the take-off. Only the engines are providing the forward thrust, which is totally not connected to any conveyor belt type of runway (it will only impact the rotational speed of the wheels, not the airplanes forward movement)

[@sirBrouwer]

It will be a problem. If the belt and the plain are moving in the exact same speed in the opposite direction. the plain needs a forward motion in order to get the air under it's wings. If the belt is moving at the same time the same speed the other way. the plain in total would have a movement of 0, (zero) it is motionless only the. in this case the positive force and the negative force cancel the other. however real life dictates that this is impossible ether the aircraft is reacting to the belt or the belt is reacting to the aircraft. even a delay of 0,0000000000000000000000000001 would mean that motion has been made.

[@stephenrowley4171]

@@sirBrouwer it's not speed it forces.

[@brandnewcreative]

It’s amazing that someone can be so confidently wrong. As the wheels spin freely and independently of the plane, the jet thrust will move the plane forward and the wheel/conveyor speed with increase as the plane moves along to take off velocity. Because the wheels of the plane spin freely, they can essentially be ignored.

[@parrotbrand2782]

The plane has to rest on the ground when the engine is getting up to speed. The conveyor belt will influence its movement. As the plane creeps forward, the belt pulls it back, so it never gets a chance to accelerate to a speed to generate lift. This is different from a frictionless surface, where wheels do no matter. The wheels can spin freely and the plane can still take off. This is where the ground actively pulls you back when you try to creep forward, hence u will never gather enough speed to lift off

[@tedwalford7615]

​@@parrotbrand2782Just how does the ground pull the plane back? The ground/belt and the airframe have no fixed connection in the direction of travel. In fact, a reverse-running belt will spin the plane's wheels FORWARD!

[@compulsive_curiosity]

Draw a free body diagram, the ground cannot do work on the plane in this way, but the planes engines will still do work

[@olican101]

​@@parrotbrand2782the belt would not pull it back as the wheels are in freespin.

[@ral98ph]

Bro this guy is a pilot with thousands of hours and you are just an average joe, I dont even bother with your explanation cause you are wrong

[@SiHill80]

Love your videos Joe but in this instance you're wrong. The plane would take off no matter how you interpret it. The speed of the wheels and belt are irrelevant. If the belt exactly matched or even went faster than the wheels then the plane would still move forwards.

[@perendinatorian]

yeah, i think the best way to look at it is that the air is ropes being feed into a winch (jets). the plane is gonna move forwards because the jets aren't spinning the wheels they're dragging the the plane forward irrespective of the ground to wheel relation.

[@9Blu]

The problem with the question is that, if the treadmill always, instantly (causality be damned) matches the wheel speed, and the belt is reacting to, not causing, the wheels spinning, then the plane cannot take off because that condition means that the plane is, always, by definition of the question itself, stationary. And because of that, the only valid speed for the belt (and wheels) to be moving at to stay within the conditions of the question is... 0. Any other speed would have required the wheels to move at a different speed than the belt, even if just for a moment. Which would mean the treadmill did not constantly match the speed of the wheels and the question's parameters are not always true and the question is broken. So no, the plane doesn't take off because the engines are not running! It's parked at the end of the runway and ATC is asking you WTF you are doing.

[@MattMajcan]

the treadmill wont push the plane backwards, it will only spin the wheels.

[@9Blu]

@@MattMajcan if the belt matches the speed of the wheels, as the question states, then the plane can't be moving. It can't be moving because if it were then the wheels would have to be moving at a speed faster than the belt. The only way for that to be true is if the wheel speed, and thus belt speed, are 0.

[@MrBenTheBear]

The tested it on Mythbusters. The plane takes off.

[@p.c.windhamparanormalroman4339]

The Mythbusters' test was highly flawed and did not meet the parameters of the riddle. I believe it is the only test that the Mythbusters completely screwed the pooch on.

[@ItsDan123]

@@p.c.windhamparanormalroman4339 Are the parameters of the riddle the way you're interpreting them possible in the real world?

[@p.c.windhamparanormalroman4339]

@@ItsDan123 That is the whole point, the parameters can NOT be met yet they still concluded that it was confirmed.

[@ItsDan123]

@@p.c.windhamparanormalroman4339 They can't be met the way you're choosing to interpret them, but it's still a red herring. You can't slow down a plane by spinning it's wheels faster beyond ludicrous excesses involving exploding tires, so possible or not the treadmill can be ignored.

[@mtb8300]

@@p.c.windhamparanormalroman4339 How is the test flawed? They put a plane with a 25mph takeoff speed on a mile long tarp moving the opposite direction at 25mph, the plane took off.

[@quenchize]

If you turn scenario 1 around. Start at the end of the runway and move the aircraft backwards with the conveyor. With no thrust it moves backwards. But in order to remain stationary it only needs to produce enough thrust to compensate for the friction in the wheel bearings. Thus in either Scenario this is the only backwards force acting on the aircraft. The only way it won’t take off is if the conveyor is moving so fast that the bearing friction matches the thrust which is absurd. In both cases the aircraft takes off with its wheels spinning faster.

[@MrDefreese]

The conveyor is essentially adaptive to wheel speed. He explains it in not so great fashion because it’s a subtle difference. In his second example, he provides the explanation of a conveyor with a constant speed which would of course allow takeoff. A conveyor that always exactly matches (rolling) speed, there is no velocity change.

[@Siatkowkarzadzi]

​@@MrDefreese Scenario 1 - aircraft will not move ONLY as long as thrust force is less or equal to the friction between the wheels and the belt. If thrust will exceed the friction, the aircraft will start moving (tires will start slipping/skidding on the belt)

[@MrDefreese]

@@Siatkowkarzadzi correct. Implicit in this example is that the wheels roll (freely) and excludes add-on items like busted bearings, absurd headwinds, etc. boiling it down, this is a basic cart and wheel physics problem where we are given unity for linear speed of the conveyor and the rotational speed of the wheels.

[@georgogiannakis6123]

@@MrDefreeseonly if the wheels eventually fail. But if we’re assuming the conveyor is magic and can sustain infinite speeds, and we assume the wheels can sustain infinite speeds, they neutralise and the thrust still pushes the plane forward.

[@SamDeMan1981]

Forgive an old fool but how exactly does the conveyor belt matching the speed of the wheels cancel out the thrust of the engines? This is the bit I really struggle with, the wheels play no part in propelling the aircraft forward. Air is sucked in, forced out and the conveyor's speed doesn't alter the thrust produced.

[@ChrisFranklin.2260]

He’s wrong on the first case. It would still take off. He’s thinking of it like a car.

[@Professor-fc7vc]

@@ChrisFranklin.2260 hes not. If the conveyor belt was able to completely match the speed of the wheels, it would have no forward motion in reference to the air it is trying to use to take off. This is completely impossible in real scenarios due to a number of factors, but the baseline assumptions of the first example would mean that the plane would not be able to make forward progress and move through the air which it needs to take off

[@ChrisFranklin.2260]

@@Professor-fc7vc I'm still not convinced. His arguments for the first case did not seem well fleshed out to me. There's still nothing to cancel out the hundreds of thousands of pounds of thrust on the body of the aircraft. Doesn't matter what the wheels are doing, or what the speed controller for the belt is basing its output on.

[@MrDefreese]

@@ChrisFranklin.2260 thrust just makes a mass go from one speed to another speed. That’s it. We know a (hypothetical and absurd) conveyor can reach any speed possible so it’s just recognizing that such a device can put the total system in equilibrium. No net speed at the wheel axis.

[@alexwilliams7836]

If the thrust of the plane pushes the plane forward and spins the wheel, there must be a delay for the conveyor, because the plane must be moving forward for the wheels to spin. If the plane isnt moving forward, there is no friction to the ground causing a rotation of the wheels, thus we must assume the conveyer has partial friction, the wheels skip, and the plane takes off.

[@grantkendrick277]

Straps CRJ 200 behind a really big fan Me: “guys I made an expensive kite”

[@rogerbarton497]

You could use wind turbines, when they're not blowing aircraft into the air they can carry on their normal function of generating power. Or why not use a catapult? That would be brilliant for short take-offs from ships, then catch them with a very strong elastic band when they land. Once the plane has stopped, the elastic band will pull it back to the start of the runway ready for the next takeoff.

[@grantkendrick277]

@@rogerbarton497 better yet remove engines from the aircraft entirely for short haul flights and just use big gliders and glorified slingshots. If you’re an adrenaline junkies we can just put you in a padded ball and launch you up to 60 miles away into a net, and hope the wind doesn’t change enough to cause you to...miss

[@rogerbarton497]

@@grantkendrick277 It's strange how the simplest ideas are the best. I'm sure we could engage the services of top snooker and billiards players to solve the problem about getting the balls in the correct net.

[@wadsefrgthzjkl]

The plane could take off, if the tires dont explode. you Accelerate by pushing air the ground didnt matter..

[@kristian4559]

if the plane isn't moving air isn't flowing over the wings and no lift will be generated

[@DIBOYOU]

indeed, the forward motion of the airplane is provided by the engines only, as long as the wheels don't provide enormous friction (which is not the case on the conveyor belt) the aircraft will have enough forward motion (=lift) to take off

[@kristian4559]

@@DIBOYOU well isn't the idea of this conveyor belt that it in some magical way cancels out the forward motion of the airplane while keeping the wheels spinning? if it is just a regular conveyor belt then i get your point, the wheels would just spin a lot faster than they normally would and the plane gets the forward motion relative to the air around it it needs to lift off.

[@shaunhorton5619]

@@kristian4559 No, it doesn't say that the conveyor stops the forward motion, only that it spins -exactly- the speed of the tires in the opposite direction. That this would cause the plane not to move is a fallacy, one most people fall into because we're used to vehicles which are driven by exerting force against a road.

[@TheOneAndONLYSensei]

i like how u explain everything super clearly

[@thomasstewart9752]

ok, there are a few questions hidden in this thought experiment, and all are a problem of the relative motion of three objects, the air, the ground, and the plane: 1. will a plane take off if it is held in place by a conveyor belt keeping it from moving forward by exerting enough force on the wheels that the wheels exert enough force on the plane to prevent forward movement? if the plane can move the air past itself fast enough, it will take off. if the plane can't do that, it won't take off. if the air moves enough, the position of the plane relative to the ground doesn't matter. the plane can take off without moving forward, as the air moves fast enough to lift the plane 2. will a plane take off on a conveyor belt designed to keep the airplane in the same position relative to the air? if the air and plane aren't moving relative to each other, it doesn't matter how fast the plane moves relative to the ground, it won't take off.