Can You Figure Out The Hour Glass Buoyancy Problem?

[@ClaeFace]

If there’s one thing that these videos have taught me, it’s how cool magnets are

[@qaywsxefb]

He literally used telekinesis as if its on a daily basis for him. Maybe the magnets are just to hide evidence 😂

[@vripscript]

and kettlebell weights are good for holding flip flops

[@banditosdetiempo]

Merry go rounds?

[@samiulbashir9252]

কিন্তু

[@AmericanChoirboy]

He must think they are super cool, too. because he kept pointing it out

[@skube587]

This dude is litterly doing every single experiment we wanted to do as kids but, we couldn't.

[@randaranatunga7259]

Agree

[@martial-guy_235]

i think i am a grown-up now as i know the reasons for his observations

[@necaton]

why couldnt you?

[@Sam_on_YouTube]

And some that we can. During quarantine, I took my kids to a field with some strong magnets and found a couple of tiny meteorites.

[@bartoszskowronski]

I thing the video is wrong! I think friction is minimal but CENTER OF MASS matters. In sand up falling down center of mass going down. we see glass not moving but center of mass do. If I am wrong do glass with sand on one side and don't allow sand go to second side. if friction matters then sand up then glass will float, if sand down glass will sink

[@karma_yogi_42]

well put together. he took a seemingly boring thing and turned it into a mystery

[@banditosdetiempo]

The phrasing in his introductions was classic.

[@MadScientist267]

Now if we could just get things explained not 42 times in the same video. There's only about 1 minute of actual content in this... And it's good content... He just says the same thing over and over.

[@banditosdetiempo]

he leaves enough unsaid though.... good for inspiration and ideas.

[@zeuxlaught2797]

that wasn't boring

[@prboric]

@@MadScientist267 He literally has a 1 Min Versions of his experiments channel

[@jnhrtmn]

Vibrate the host tube walls to release the friction by bouncing off of the sides.

[@jerkofalltrades]

No matter how much you vibrate the tube, the problem is the tube is too narrow for the hourglass to ever flip over.

[@dennisolsson3119]

@@jerkofalltrades but the friction would momentarily go away as the glass bodies separate.

[@MEBVishwaS]

Or tie a payload at bottom with a string and tune the density of fluid one weight of sand to support that load and it shouldn't flip over.

[@PBMS123]

@@jerkofalltrades But it doesn't have to flip over to sink, if it did, then friction wouldn't be what causes it to float.

[@Qexilber]

He forgot to show us one thing, what happens if you start with the hourglass at the bottom of the tube? He could’ve pushed it down as he even says in the video with a glass rod

[@shadykermit2187]

Exams ask you these kind of questions, and then teachers expect you to solve it in *3 minutes*

[@sankalps17]

Life is Unfair 😅

[@voidex136]

idk i solve this very fast just by looking on it and i dont consider myself a smart person. omg does that mean that humanity is not very smart?!

[@davidscott5903]

I did it in 3 minutes.

[@velicanmaria7772]

@@voidex136 imagine being this insecure

[@granny2677]

Exactly dude, these competitive and school's theoretical exams have murdered totally applications based subjects like Science and computers.

[@Ali107]

The Hourglass can actually be used as a timer to press a button underneath the water tank.

[@romano6162]

this is some saw torture machine type shit

[@s_gaming71]

the hourglass itself is already a timer

[@xaigamer3129]

@@s_gaming71 yea ok but it auto press button (without camera robot thingy) you should probably become smarter than me if you want to outsmart me i guess lol

[@D-B-Cooper]

Thanks for the new trigger for my bomb.

[@MadScientist267]

Think I'll just use... a timer 😉

[@TooMich]

I thought it would be something like how the center of buoyancy would be lower when the top boards fall, and it would be in slightly denser water because of the gradient and that would be enough to keep it up, then when the sand goes down the center of the points he is slightly higher

[@joescrivano5285]

I agree with everything you said other than the water getting denser. The water pressure increases the deeper you go, however the density remains the same as water is essentially incompressible.

[@oliver_beres]

I thought about this too. When the pressure is a little higher it pushes it more upwards.

[@tpros6289]

Thats a pretty cool trick.

[@damartimantilla]

The center of buoyancy has nothing to do with the amount of buoyant force. The density of water is the same in the container so buoyant force given by Archimedes (only displaced volume matters). This is the reason why the experiment is perplexing at first glance: Buoyant force is the same whether the hourglass has sand on top or bottom. The only explanation is what he said in the video, friction with the container walls

[@nattycaptainanavar8319]

@@damartimantilla hi. Overall buoyant force for the hourglass is the same as you said but the centre of neutral buoyancy changes slightly as the sand moves from top to bottom. That’s why it wants to flip over.

[@bh4rg4v21]

I click on his videos faster than my school classes 🤣

[@pranavramnedi9821]

Exactly

[@randaranatunga7259]

We probably learn more from these too

[@harshpandey6537]

@@randaranatunga7259 Sri Lankan bro ?

[@necaton]

i click on everything faster than my school classes xD

[@codylee1682]

@@necaton even dude porn?

[@ArjenZwerver]

Is it really the friction that keeps the hour glass from sinking? If you look at the drop on @1:50 then it looks like it's sinking first. But then the buoyancy takes over and stops the downward motion almost making it look like it wants to go up again. Maybe this is where the friction comes in to prevent that from happening? I'm really curious what would happen when you put the hour glass in (sand in top) and then pull the hour glass down with a magnet then releasing it. Will it try to float to the top first? Or will it just stay at the bottom? My theory was: If you divide the hour glass up in 2 sections (top and bottom) and look at the buoyancy created by each of those sections (both without sand) you will see that the top part creates less of it then the bottom part due to the pressure differences in the water caused by a difference in depth. So lets assume: "A section filled with sand will only provide half it's original buoyancy". When the sand is in the top it will lose less buoyancy so it floats. When the sand is in the bottom it will lose more buoyancy so it sinks. Would that make sense?

[@human.earthling]

I thought the answer was what you wrote in your theory.

[@PunnamarajVinayakTejas]

If you put the hourglass with sand at the top and drag the hourglass all the way to the bottom, it would stay wedged there. Your theory doesn't exactly hold up for incompressible fluids like water (it actually does hold up in fluids where density increases as you go lower down) because the buoyant force on a body depends only on the volume of the body and the density of the surrounding fluid. If both sections were empty, then they would have the same buoyancy because even though the lower section is at higher pressure, the pressure difference across it is the same as that across the upper section, being equal to the product of fluid density, gravitational acceleration, and depth difference.

[@ArjenZwerver]

@@PunnamarajVinayakTejas I'm sorry for asking stupid questions and wanting to find out in my own way. Clearly you already have all the answers. 🤔

[@PunnamarajVinayakTejas]

@@ArjenZwerver bruh. I appreciate you trying to find out. I do have a lot of answers with this phenomenon and I wanted to share and help people learn. I apologise for getting so carried away I didn't notice the condescending tone of my comment.

[@imd12c4advice]

No, the weight of the sand and the "bouyancy" are totally seperate things. The presence of sand in a particular half has no effect on the force the water exerts on the outside surface of the glass.

[@kreynolds1123]

We can say the buoyancy is for all intensive purposes, static and unchanging. That means adding friction does not change the buoyancy. And neither would we say the heavyer than water upside down submerged hourglass is floating. But we can say that the buoyancy counters enough of the force of gravity, so that friction may hold it in place, untill the force from the pressing on the sidewalls (created by the hour leverage action created by center of mass along an unbalanced hour glass and buoyant forces acting on the hourglass), reduces enough that that lever can no longer provide the pressure nessesary to generate the friction nessesary to overcome the downward force.

[@HereToSin]

Great explaination! I would like your thoughts on the weight being the same in both the cases. I was thinking that if the hourglass is inverted and sand is allowed to fall, wouldn't there be the impact force of the particles falling when they hit the bottom surface, adding more forces to the weight. The greater the height, the more this effect would be. What do you think about this?

[@kreynolds1123]

@@HereToSin My thoughts. When a sand particle drops from the top, there's a moment when the weight of the house glass is reduced by the weight of a sand particle while the sand particle is in free fall. When the sand particle lands, the weight of that sand particle is again added to the weight of the hour glass. additionally, it's possible that with friction and dry sand, electrostatic forces may complicate the process. Finally, while falling, the sand particle accelerates gaining momentum so that on impact, much of that impact goes to shifting other sand particles where much of that energy transferred into making heat, and a tiny a fraction of it gets transferred to the hourglass. So, for a brief moment a collision with a sand particle may make the hour glass appear a little heavier than the hourglass weighs after the hourglass time run out, but it's only going to be a tiny fraction of the weight of a grain of sand, and is probably offset to a large degree by other grains in free fall.

[@HereToSin]

@@kreynolds1123 Thank you for the insight. Have a great day!!

[@jellina2000]

Hi Recently I noticed a weird thing around me There's a electric wire outside my house, it's straight and has some slope When it rains water droplets since it has more adhesive force moves along the wire downwards But water droplets from the other side move upward along the wire How this happened I am sure the wire is straight and has a slope

[@vasuyadav2931]

What is the "other side" you are referring to here?

[@jellina2000]

@@vasuyadav2931 I meant from other end of wire which is at a lower level than the first end of wire which is at a upper level

[@Leverguns50]

That was a really neat experience, it’s almost magical.

[@zaahidmuhammed207]

I feel like a genius for guessing the reason for it flouting and not sinking correctly before he told us

[@bwood6337]

I completely overthought it and guessed it was something to do with atmospheric pressure.

[@turtleduck9198]

You go my guy. I never even thought about it.

[@DarkJinxWasTaken]

Cuz more air like boat

[@keiji1531]

I guess it correctly before he says that

[@revimfadli4666]

I watched it somewhere else, with a water tube with an hourglass inside, that when you flip, it stays until the time runs out, then floats/sinks

[@klschofield71]

I would like to see this experiment with a tube, unable to be blocked by sand, connecting the top and bottom, so as to prevent the possibility of a pressure differential, which is what I belive is causing it to float. As the vial is flipped, the motion of the sand tries to push the air out the other end, but since it's sealed, the air subsequently ends up on top of the sand just prior to the sand sealing off the choke point.

[@takix2007]

There will be a pressure differential, because there will be a column of water in a gravity field. Also, it is not the pressure differential that makes an object float, it is gravity (as in, all objects tend to fall/go down, but the heavier object replaces the lighter one at the bottom, so the lighter is "pushed" upwards).

[@CMZneu]

I thought there was something cooler going on for a second... i guess i never imagined that glass against glass in water would generate that much friction.

[@banditosdetiempo]

Nope not that cool...... but still... pretty magical. No one ever stares at the movie projector.... instead they are always looking at the screen. 😊

[@Observ45er]

It is not "so much" force. It is a tiny amount. That is why he makes it JUST BARELY floats. Informative, but deceiving by design. At the beginning it is disingenuous to say that it 'floats'. It is very obvious that is is NOT "floating".

[@bartoszskowronski]

I think friction is minimal but CENTER OF MASS matters. in sand up falling down center of mass going down. we see glass not moving but center of mass do. If I am wrong do glass with sand on one side and don't allow sand go to second side. if friction matters then sand up then glass will float, if sand down glass will sink

[@wradex3212]

I've learned more from him these past months than I have from my classes in a whole year

[@schmarcel4238]

if you had to write an exam about the topics he showed in his videos you would fail horribly

[@athul_c1375]

before I answer the question let me write about my sponsor

[@Banditt42]

Refreshing to get educated without being indoctrinated into the Liberal agenda.

[@Ugg_Son_Of_Thogg]

@@Banditt42 oh no not the rainbow in my physics class oh god

[@hmmmtietmetmosterd]

That could be a "you" problem tho

[@Amira_Phoenix]

and can we just take a second to admire how nonchalantly this guy is handling his gym weights? 💪

[@ripmorld9909]

1:36 I propose the theory of this is the sandglass wants to flip over because the center of mass is not as low as possible. As it flips over the head sketch the container wall, as the fiction generates an upward force.

[@PunnamarajVinayakTejas]

Precisely. This is like an inverted pendulum, in an unstable equilibrium, so it will always tip over.

[@TechnoSan09]

I think it has to do with some density distribution Like the principle of ship floating And also it has something with center of gravity (Forgot most about it which I learnt in mechanics in last year in school 🤦‍♂️)

[@zlaundry]

That's what I thought too

[@2nd-place]

Would putting a hydrophobic coating or some kind of lubricant on the hourglass to lower the friction make it sink right away?

[@princehalder6219]

What i think is if hydrophobic liquid is introduced on the outer surface then the tube might go into an equilibrium wrt the water in the larger tube, but as the water is been pushed alway it stricks with the the inner wall of the larger tube and the force revert backs the smaller tube (mainly it might give us the same result as shown here my hypothesis!!)

[@thomashan4963]

Dude really knows how to teach and explain ❤️

[@RANDOMSWIPE]

I'm gonna ask about this to my physics teacher and make them confuse for a bit lmao

[@countofst.germain6417]

This won't confuse anyone with half a brain. It certainly won't confuse your physics teacher. Unless you don't explain that it will only work in a tube or something with a diameter or width smaller than the height of the hour glass.

[@Bui1tDifferent]

@@countofst.germain6417 I got confused for a second ..

[@countofst.germain6417]

@@Bui1tDifferentwell I was confused at the start, because what he was saying didn't make any sense, but I didn't realise it was touching the sides. He was just trying to make it sound tricky, but in reality it's very basic.

[@michaelcantu6071]

@@countofst.germain6417 that’s the whole point of it; it’s a trick. Most people aren’t going to notice that the hour glass was touching the sides. The best part of his videos are when he explains the tricks and everything starts to click.

[@banditosdetiempo]

@@countofst.germain6417 classical magician technique employed in the way he framed the introduction. 👍

[@jbirdmax]

Fantastic presentation as always!! You somehow always manage to keep our attention no matter how mundane the subject matter. A true master of the craft.

[@AttractionSpot]

Hey not to be rude or anything but isn't the sponsor for this video a direct competitor to your own kits? Or maybe you felt it would help you out more using this sponsor? Was just wondering as someone getting more info about sponsors and what has worked and what hasn't with people. Anyways love the video. You always have very interesting videos that are kind of science related but fun.

[@tejasbharadwaj7830]

Well I don't think he takes that in such a business minded sense. And that's good science should be as non profit as possible

[@DrRiq]

Are his kits still a thing? I was thinking of getting one but I assumed they had ran out

[@aadityasanjeev5776]

He had Promoted Curiosity Box by Vsause.. He probably doesn't think like that.

[@Scrungge]

It's all science why not? People thiink too much in bussiness terms...

[@StreakyBaconMan]

I thought his kits were like " build yourself a vacuum chamber at home" type of thing that you just buy, and these other boxes appear to be more of a subscription service where you receive regular kits to preform specific experiments designed to be accessible to children. There may be a little bit of overlap in the market, but I'd dare say not that much. One you'd buy if you just want your own home made vacuum chamber, the other you would buy if you wanted to get something educational to keep your kids entertained and get them curious about science.

[@Aldo.flores]

It’s not about weight, the weight itself never change cause you have the same mass amount on the system. The sinking effect it’s related to the weight location in relation of the center of mass (gravity center), for a buoyant the weight distribution affects directly the way that it behaves, if it’s over the mass center on the same flotation axis it have positive buoyancy but it becomes very inestable, if it’s closer to the mass center it became neutral buoyancy but it turns below the mass center then it have negative buoyancy. That’s the reason why divers have the weight belt over the waist and in a very similar way submarines after fills special ballast chambers to sinking, could control its buoyancy by moving back and forward a kind of pendulous weight from the center on the gravity center.

[@rwjensn]

I don't think the friction is the reason, I saw it flote even when it wasn't touching the walls. But I think it's because of the pressure difference as you go down the tube.

[@shailendradeota6701]

Or due to change in metacentric hight initially as sand falls down it becomes unstable and sinks down

[@ElVerdaderoAbejorro]

It was always touching the walls, it's just he changed the angle at the beginning as to not be so obvious.

[@rwjensn]

I want to see this done with a string attached to the end so it can't flip, only sink when the sand moves down.

[@sanchaysachdeva]

Hi, I just thought of a fun experiment. Suppose an object is falling in a tube. As soon as it reaches the centre. Flip the tube upside down so that it will fall from the other side. Doing this keep the object in a the centre(or a small range). What is actually happening? It could be better if observed with a magnet falling through a copper tube... I am already curious to do the experiment by my self. But i don't want to spoil your lovely and in depth explanation. I would be glad if you make a video on this experiment. Love your videos💛

[@PragyAgarwal]

From the video it wasn't really clear that the hourclass was touching the sides of the tube. Also, even though we see the hourglass stuck in one place for a brief moment, the sand is moving downwards, which means the center of mass of the hour glass is actually sinking.

[@larrybud]

Yep, this is a fail video for sure.

[@blueredbrick]

What ? Tss the friction on the wall ? Anticlimatic..

[@PPpeepi]

You are wrong He was not giving the side view at that point

[@michaelcantu6071]

Yup. He pretty clearly explained the second part of your comment in the video…

[@madhavvarshney3912]

One of the best practical science channel with always mind blowing ideas. Keep it up

[@barackobama7569]

Me who has been learning online for 2 years already: *ah yes sand is sand*

[@shishka67]

You missed a big part of the conclusion, that the friction force keeping it up is directly proportional to how much sand is in the top half. In other words, this will work with any size hourglass, because the heavier the hourglass, the more friction force is produced on the cylinder wall to keep it up as it tries to tip over.

[@apbosh1]

isn't there a limit to how much friction glass on glass can offer?

[@shishka67]

@@apbosh1 I don't think so. Friction is always proportional to the force between the two surfaces.

[@stephenlepage]

Great video, but calling it out that this was sneaky! The first two demonstrations at 0:40 and 1:24 happen to have a camera angle that helps to conceal the hourglass leaning on the inside of the tube. In the third demonstration at 1:52, we can see the lean, but the hourglass is moving around so freely that it appears to be floating and isn’t obviously rolling with continuous static friction. The fourth demonstration at 3:50 is a different experimental rig with rubber o-rings, and this change of experimental setup introduces the new variable of the frictional properties of rubber to consider. Only in the fifth demonstration at 5:02 (the reveal) do we see a demonstration with 1) a wider tube so the hourglass leans more, and 2) a side-on camera angle where the frictional forces are more apparent. Sneaky!!! P.S. At 6:06 you said “and whenever it leans against something, then that introduces a new static force or a static friction that’s pushing it upward and it’s helping ‘increase its buoyancy’.” To be pedantic, it doesn’t actually ‘increase its buoyancy’. A free body diagram would show the same downward force due to gravity plus the SAME upward force due to buoyancy, but with an additional force due to friction which brings it to net zero.

[@adamaoun1535]

All i see is a butt hurt science student that thought he could easily figure out what was going on but still got tricked🤷‍♂️

[@zioqqr4262]

i frequently find myself a but frustrated by the topics you choose, but that ad reminded me that when i was younger i had to start somewhere. so thanks for making these interesting phenomena so easy to understand for anyone

[@stunseedbackwards1947]

What if you put the hourglass on the bottom of the tube with the sand on the top of hourglass, will it float up or will it stay floating at the bottom of the tube?

[@xxdragonmage]

Bottom

[@banditosdetiempo]

Good question. I noticed a hinge on the cylinder mounted on the wall. Is a pivot hinge?

[@zecuse]

For those doubting this is due to friction, notice at 3:50 that the hourglass is dragged to a halt after it's fallen into the flipped water. Eventually, the center of mass of the hourglass moves low enough to "stand" the hourglass back up (3:56, but it's hard to see due to all the shaking) enough to release it from the walls. The change in the center of mass is moving the hourglass from an unstable to a stable equilibrium.

[@GMCLabs]

Cool, this is the first time I've seen this and I was able to figure out the answer before you gave it!

[@sharmilavilluri6772]

Yeah, me too

[@cryptfire3158]

wow, (not sarcasm).. i'm wondering if you guys are super intelligent. Because.. i used my brain till smoke came out of my ears and i couldn't figure it out.

[@trevvrun]

Wow (sarcasm)

[@cryptfire3158]

@@trevvrun i sounded sarcastic i guess. But, it is pretty hard to figure out the answer, at least for me, till he explained.

[@cetyl2626]

Whew.... 🤯. I really thought my understanding of buoyancy was wrong... you really had me there. I knew something was up when you demonstrated turning it upside down and were more careful about it. Good one.

[@minhthai4264]

Moral of this video: *Never despise an hour clock, or it will despise you back*

[@davidonfim2381]

I don't get it.

[@banditosdetiempo]

Remember the time when we walked across the entire universe in just three steps?

[@aaronredd5794]

I've been wanting an explanation on this little ESC demo for years! Thanks!

[@carterwalters5915]

Dang, the video dropped 27 seconds ago? Earliest I've ever been. Thanks for the amazing videos brother

[@LeventK]

@then ur awesome shut

[@Mr.GuptaShivam]

Hello sir, Love watching you experiments. I this phenomenon from my POV one of the reason for friction due to fluids can also be due to more air inside the lower end which creates more buoyant force in comparison to less air in the lower end... because water puts more hydro static pressure to the vacant space at greater depth.. Keep doing such experiments sir😊😊😊

[@danagillam]

But since the sand container is not deformable, so there is no way for the water to know where the sand is. The boyant force does not change based on the orientation of the submerged object. Even in a compressable fluid that gets denser with depth. Laying flat the container expereinces 5 newtons of boyant force for each CC of water displaced. Standing on end the higher portion exeperiences lower boyant forces, the the lower end experiences higher boyant forces. resulting in the same average boyant force. My explanation is: the weight does change slightly. When the sand is at the the bottom all the sands weight contributes to the systems weight. But when the sand is at the top and some is falling, the falling sand does not contribute to the weight. If we had a ball in a box, the ball would contribute to the systems weight. If we suddenly turn it over, while the ball was falling in the box, the box system would be lighter since the falling ball is not contributing to the weight. The newly turned over device has a long column of falling sand and therfore 100 grains are in the process of falling and not contributing to the weight. As the sand builds up in the bottom, the length of the column of falling sand decreases (now 50 grains in the state of falling) and thus the weight of the system increase since fewer grains are in the state of falling.

[@usmcbrat2]

Technically, the hourglass is "heavier" when the sand is at the bottom, in that more of its mass is closer to the rest of Earth's mass... which means that the gravity attraction between Earth and the hourglass is greater. But of course that effect is far smaller than the precision of any measuring method you would have to detect it. Great video. Thanks!

[@mohitjain6442]

So impressive!!!! I want you to make more videos as you can explain things more deeply than in shorts.

[@zlaundry]

I thought when there was more air and less sand in the lower half, the hourglass had more buoyancy due to higher water pressure, similar to how a pool float becomes harder and harder to keep underwater as you push it deeper.

[@ToMeK3001pro]

well, glass is not elastic,

[@allylilith5605]

a pool float doesnt become harder to push down the deeper it is for that reason. buoyancy is always the difference of an objects weight and it's volume times water weight. So there is always the same force pushing it upwards no matter how deep it is. It probably feels that way, because we as humans are weaker in the required positions to push it deeper

[@zlaundry]

@@allylilith5605 That make sense, but it doesn't seem quite right. I did a quick google search, and could not find any info on the topic. I think The Action Lab should try this.

[@AmeshaSpentaArmaiti]

the pool float pushes you up as much as you push it down, so it becomes harder because you aren’t rooted to the ground.

[@countofst.germain6417]

@@allylilith5605 bruh, the deeper you are underwater. the higher the pressure, so the object has to displace more water the deeper you go. It's called the Archimedes principle: The buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid the body displaces.

[@rodjacob1000]

If you do this with an hour glass that is slightly less dense than water then it will work the other way round- Invert it so the sand is at the top and push it to the bottom of the tube. As the sand fills the lower chamber the friction against the side will decrease and the hour glass will rise. I spent some time in the early 1990s making these- with two parallel tubes- one with a floating hourglass and one with a sinking hourglass. When the entire structure is inverted one hourglass gradually sinks and the other gradually floats. We filled the hourglasses and paired sinkers and floaters with similar delays. This created the illusion that one hour glass was somehow influencing the other. We sold these through a toy and puzzle outlet in London.

[@robinraj9788]

That's is also cause Metacentre is changing as well the the c.g of that Hour glass.

[@sambhurajasekharan9553]

That's why he chose a smaller water column instead of something with larger dia. We could also see him keeping the hourglass closer to the wall so that the tendency for it to flip vertically becomes not so obvious. Great experiment ,showing how forces play out.

[@wimbraber944]

I thought that less “length” or “height” of sand being in “free fall” and thus “weightless” was contributing to the sinking...

[@wernergraff]

Exactly the same line of thought I was following. It certainly results in a weight difference. Though it‘s probably an extremely tiny difference. I guess he would not have arrived at balancing to this accuracy with the wire he wrapped around the middle of the hour glass.

[@QuantenMagier]

#metoo I also had this thought first the problem is the free fall accelerated sand then hits the bottom and pushes the hourglass downwards again giving its kinetic energy back to the hourglass. :D

[@PunnamarajVinayakTejas]

I thought so too, but I realised that the total momentum of the system isn't really increasing, since the sand being brought to an abrupt halt at the bottom just gives back that force. So maybe while the flow is still increasing this could hold up?

[@callmepopyallfather2473]

I was thinking the hourglass would weigh more when the sand is at the top due to the potential energy, similar to a compressed spring.

[@6F6G]

It probably does but the difference would be too small to measure. A small gas bubble forming on the side of the tube would affect the buoyancy more.

[@Ktulu789]

What about the little amount of sand that is free falling? As more sand reaches the bottom, the distance to the pile is shorter so the sand in the air is less, hence there is a slight change in weight.

[@zlaundry]

I think that would have some effect, but at such a small scale it doesn't do much.

[@peterwright4656]

Yes you are correct, And the explanation is wrong.

[@LucaPro02]

kzbin.info/www/bejne/gHq5o4SHas-FosU

[@agent5518]

Internal forces can never do anything. They always Cancel out

[@Ktulu789]

@@LucaPro02 you are the best! Thanks so much!

[@eliramh]

It's nice to see that the hourglass never actually moves upwards, but rather stays in place until it starts sinking.

[@Bluelightbandit]

Without even watching the video, I would assume that the location of the chamber of air makes all the difference. Weight will be the same. I'll finish the video to see if I'm wrong.

[@bugmaster05]

Nah, its the friction,

[@PPpeepi]

Huh you are wrong...

[@michaelcantu6071]

@@PPpeepi nothing wrong with having an incorrect hypothesis

[@Dooperbooperlooper]

@@bugmaster05 where IS the friction?

[@ooo3940]

This is the first tricky video I was able to figure out what the answer was before you could explain it... THANKS FOR PUSHING ME TO THINK BEYOND THE COMMON...

[@carlomassimo2005]

OMG I guessed the answer right!!!!! I am so proud.

[@Zareen686]

I really wondered about this for over a month and you got this!

[@atulyaaishwarya3550]

This guy is a better teacher than my school teacher. 👍

[@karthiksk7246]

"Let me explain what's it mean by that" Comes with a slippers on the hand

[@pzeller1]

I mean, if we want to get oddly specific, technically it will "weigh" more if the sand is on the bottom. The difference would certainly be immeasurably small though. Because if the sand is on the bottom, it's perhaps 1-2 cm closer to the Earth's gravitational center, and thus will experience a stronger gravitational attraction. Like I said... oddly specific.

[@T0MT0Mmmmy]

YES. That are exactly my thoughts too. It has always the same mass, but the weight depends on how near the grains of sand are to earth ... And it's getting heavier and heavier the deeper it sinks. :-)

[@publiconions6313]

I was also thinking along those same lines!!!.. though, I was thinking realitivistically -- it technically does *mass* more when the sand is at the top (yes, weighs less, but masses more) -- the sand at the top has some intrinsic potential kinetic energy and would literally mass more in that configuration according to Einstein... though it would be infinitesimally small. I hadn't thought about your point, though- I wonder if they cancel out?.. probably yours is stronger.

[@publiconions6313]

... just thinking about it even more -- as the sand falls, it converts that little bit of extra kinetic energy to heat energy as the sand hits the bottom and jostles around with the sand already at the bottom -- that heat dissipates through the water and escapes from the "closed" system of the hour glass... only reloaded when you exert force again to flip it back over. Gosh physics is cool!!

[@jpolowin0]

@@publiconions6313 The warming causes a slight expansion of the glass bulb, making it displace more water. :-)

[@publiconions6313]

@@jpolowin0 ooooh.. yah, good point!

[@Kodykenway]

I saw the title. My engineering brain said buoyancy should not change. Had to click. Then I saw the tube it was in and jacked on an angle. Good video.

[@LeventK]

"He's a little bit confused but he's got the spirit."

[@ratboyisback]

I understand him but still very true

[@jakeflint8041]

What

[@jewelxiat]

I don't know why this resonates with me, but there's something so absolutely beautiful about a floating hourglass in water. 😊

[@Think_Inc]

An hourglass alone is enough for me.

[@truckthiss]

Stiction. It is the amount of force required to overcome the resting friction of two objects touching each other. It isn't a force pushing upwards, it is better described as the interlocking of the molecules on the surface of the two items.

[@webbugt]

I think another way of showing that its friction is by eliminating it. Basically adding a neutrally bouyant construction (more floaty on top, less floaty on bottom, hourglass in middle) that would keep the hourglass in whatever position we choose. With such a contraption you'd be able to show that it sinks either way and friction was to blame

[@arthurmorgan8966]

5:26 Not to be a footwear nazi, but that’s a flip flop.

[@TheArgosReed]

You keep blowing my mind…and that is why I subscribed. Thank you.

[@sovietbot6708]

I figured it would flip over before you showed it. Though I couldn't explain why that was the case. I just knew from experience the heavier part of the an object will face down when sinking unless it's impossible for it to flip.

[@salvatoredigiacomo8836]

The Archimede's force acts on flow line, so the lithest part goes up as a scale.

[@neutronenstern.]

Well it turns, cause its a unstable state to have high mass up if it csn flip. Just draw two states : one where it is completly straight, and one when it is slightly tilted. When you draw the force vectors,you will see, that while it is straight, there wont be any force being able to turn it , cause the gravitationsl force pulls exactly downwards and not perpendicular to the tube. Bit when it gets tilted slighly, you will notice, that there will be a force l, that tries to tilt it more. So its unstable, cause at the point it slightly tilts, it wants to tilt more and more and more, till its flipped with heavy side at the bottom. Then it will be stable. Cause if it slightly tilts, there will be a force against this tilt, and it will tilt back

[@billbauer9795]

This is my favorite experiment on this channel. Absolutely spectacular!

[@yash_deep]

It feels good when you arrive early 😊

[@kg9266]

Tell that to my ex🥱

[@CentralAerospace]

🧐

[@jad31b]

Yes

[@varvideoassistantreferee8958]

This guys is really entertaining, ive watch him since 2019

[@VagueHandWaving]

For a split second while it is upside-down, however, some sand from the top will be in free fall without any yet hitting the bottom of the glass. It would be lighter for that split second as the falling sand has no weight. Though that effect would immediately be canceled out by it hitting the bottom or (in a perfectly stable floating) the bottom would rise to hit the falling sand.

[@medleyshift1325]

The falling sand does in fact still have weight in the hour glass frame. One way to account for it is that the sand is pushing air equal to it's weight out of the way but that air is trapped in the hourglass. The sand might not feel it's weight but the hourglass frame does. Measure an hourglass on a scale and note that the weight doesn't change. good thinking though.

[@VagueHandWaving]

@@medleyshift1325 the sand is only pushing air equal to its volume out of the way, not weight. If u consider the limit where the density of the air decreases to 0 as in a vacuum, the sand must be weightless. While the air will be pushed down slightly by the falling sand, it will also be pulled up by the lower air pressure in the top bulb as the sand leaves. While some molecules of air might hit the bottom more frequently during that phase I think that effect is inconsequential. It should still happen though, but I think the net effect is still a decrease in weight. If you consider a bowling ball dropped over a scale in an airtight box where the scale is the entire bottom face, I don't think the scale would register its weight while in free fall.

[@imd12c4advice]

@@medleyshift1325 That's only true if the sand is at a terminal velocity, which it will not be in that short of a distance.

[@harikishore2514]

I thought something like... Water pressure increases as you go down, so when the lower part is empty in addition with bit high water pressure it has maximum Boyency so it floats, as sand shift to down emptying the top, but now empty part relatively in less water pressure, it doesn't have enough Boyency to float, so now it goes down.

[@rodchallis8031]

I thought about water pressure for a few seconds, too. I'm wondering why I and so many missed the friction solution, and I'm thinking it didn't occur to us because in everyday usage, glass on glass is not something we associate with friction, in fact we might even consider it next to frictionless-- but of course, it isn't.

[@PunnamarajVinayakTejas]

So now you know that buoyancy only depends on pressure difference, not the pressure itself.

[@harikishore2514]

@@rodchallis8031 Even if the friction is zero, I still doubt the norm that it goes down.

[@memeak]

Nice sir Love from india

[@PraXii1109]

What i presumed before the explanation was given, was that, as the sand was in the upper part of the hour glass, was having a higher center of gravity, which relatively had less gravitational pull over it as compared to the 2nd setting. As we all know, G is inversely prop to 'r' squared. Thus when the sand was in the lower compartment, having a lower center of gravity. The g force acting on it was comparatively higher causing it to sink comparatively faster. However the high center of gravity also causing the system to be unstable and hence, causing it to flip over, leading to the wall friction, but that will only explain the very instant reduction of sinking time taken, but overall its the center if gravity governing how fast it will sink, in comparing the 2 systems. Im open to discussion if any. Thnx

[@osamahanged]

This was legit. Love these vids.

[@manavmnair6975]

When kept upright, the sand particles falling should experience weightlessness. When they stop falling, the mass of the sand particles must return. So maybe it is the small difference in net mass that affects the sinking and floating. @ActionLab, can you do the experiment again but this time don't allow the sand to fall to the lower chamber in the hour glass

[@abcdefgh-db1to]

It does make a difference but so marginal it would be indistinguishable. The mass of the falling sand partical is probably not even a tenth of thousandth of the weight of the hour glass. And so the difference in acceleration would be insignificant

[@archity1242]

what if you balance the sand perfectly in the top so that the glass doesnt try to flip and hit the tube?

[@sa-zq4eq]

U can't balance it perfectly

[@blueredbrick]

Yes or weigh it down with some wire or something.

[@archity1242]

@@sa-zq4eq well duh its theoretical

[@sa-zq4eq]

@@archity1242 what do u mean

[@archity1242]

@@sa-zq4eq its obviously not possible to perfectly balance the sand but if you could what would happen

[@davemcddd]

Fascinating experiment! So simple, yet so complicated.

[@BossSev38]

I was wandering if hourglass looses weight while some of it's grains are in a freefall, but it went completely different way

[@danagibbs3265]

This is what I was thinking too, but when it started falling after only some sand moved I knew that was wrong. It feels more like a trick since it's just from the hourglass sitting against the side of the container

[@nitd955]

I feel u are right 👍

[@PunnamarajVinayakTejas]

Kinda makes sense. It would only lose weight if the momentum is increasing, which is only when the flow rate of the sand is increasing

[@danagillam]

The weight does change, but only slightly when the sand begins to fall, and again at the conclusion of falling (for a split second). During the fall the loss of weight (due to the falling sand not adding to the weight) is counterd by the impact of the sand against the bottom.

[@himachal8252]

Pulling that up with that magnet was so cool

[@LVIS-a]

what I find most incredible is that an america can say "buoyancy" just fine, but when something says "hyundai", it's suddenly "hunday"

[@mcwooley]

My application of this: A sleep machine Take a balance scale, put an hour glass on one pan (heavier chamber up), and put a seashell on the other pan You can fall asleep to the shell's white noise while it is down, and stay asleep without the noise when the hourglass brings the seashell up Saturday, October 29, 2022 CE, 18:44 EDT

[@user-se5hs3ch8o]

Love from india 🚩🇮🇳❤️

[@maheshsapkal2573]

Me too

[@hillbillyohio513]

I would have never even thought that this was a thing lol, great video like always. You amaze me time and time again lol

[@testusersg]

It didn't float when upside down. It just stop moving. It can be seen that it remain stationary at different height and doesn't "float" to the top.

[@baraskparas9559]

Technically the distance from the centre of gravity of the sand and the centre of the Earth is different in the 2 conformations but your explanation is correct too with buoyancy increase of a toppling tube being an additional factor as well as the kinetic energy of the falling sand in the sand-up conformation.

[@dzarthedemon4855]

I'm sure there's something poetic you could make out of this Something about time running out, most likely

[@jackmiddleton2080]

The small stream of sand in mid air does reduce the weight though even if it is not enough to cause it to float or to be registered on the scale. The force of the sand hitting the bottom may also affect weight readings. Suffice to say though that the stream of falling sand, just before any has hit the bottom, is going to reduce the weight.

[@kevinsalmador739]

Equilibrium That's it !! What a way to learn :)

[@chimicazza]

Love your videos! You're always giving very intuitive explainations. This time i thought there was something about the depth of the air bubble. Is it possible that the buoyancy of the hour glass changes because the relative depth of the air bubble inside changes as well? if the air bubble is at a greater depth in the water tube it might be displacing a slightly denser (so heavier) water because the pressure is greater on the bottom of the water tube then at the top. if the pressure in water increases by 1 atm every 10 m it means it changes by 0.01 atm every 10 cm. So the water at the bottom of a 10 cm long hour glass can provide more buoyancy then the water on top (?) do you think it make sense? could it make a difference?

[@imd12c4advice]

The pressure gradient is what gives rise to bouyancy. If there was no pressure gradient, there would be no bouyancy force. Also it cannot create "more bouyancy", it just creates the bouyancy.

[@jackfables3470]

This reminds me of the Mythbusters episode that explained how Jack and Rose from Titanic could have both easily been saved : Just tie the lifejacket to the bottom of the plank, to allow it to support both Jack's and Rose's weighs simultaneously, instead of sinking. Basically, have the heaviest part on the top (Jack and Rose - or, in this case, the sand) and the lightest part on the bottom (the lifejacket under the plank - or, in this case, the still empty half of the hourglass).

[@-TheRealChris]

That's not what happening here, watch till the end for the explanation.

[@jackfables3470]

@@-TheRealChris True, but I'm just saying that it reminds me of the same experiment. The forces at play are not the same, but it still brings back those memories : in both cases, the fact that the heavier or the lightest part is either on top or at the bottom influences the end result and the buoyancy. Whether it is ultimately due to friction (like here) or another cause (like in the Mythbusters episodes), it still triggers the same 'Hey, I saw something that looks a bit like that, before' reaction. And, yes, putting the heaviest part of the hourglass on the top will increase buoyancy. It won't increase it just by itself : It will increase it indirectly, by causing the situation where friction is forced to intervene. But I can understand how my wording could have sounded a bit ambiguous, in my first post.

[@mkjaiswal11]

How I will take out the hour glass from the tube: By flipping it Action Lab(Takes it out using a magnet): I am 4 parallel universes ahead of you

[@arvetis]

I've never seen a man ask the same question over and over for five minutes and put an advertisement in the middle of it. Congratulations?

[@firenhell02]

Air displacement. There's a little gap inbetween each particle of sand and as each grain of sand falls, the air underneath rises to the top tube. The air under the sand has more resistance to move up and as the sand becomes less and less, the more the air can move up. Same thing with water or any other liquid as well as particles.

[@ehtuanK]

Actually, the hour glass has a tiny bit less weight when the sand is on top, because the falling sand doesn't exert a force onto the scale while in free fall. But since the mass of falling sand at any moment is so miniscule, it's difficult to measure the difference.

[@eliramh]

It also weighs less because it's farther away from the center of the earth...

[@Tschemba]

This also explains why it suddenly sinks rather than gradually. If the buoyancy would change the hourglass would sink slowly to the bottom as the sand falls. Now it suddenly doesn't touch the sidewall anymore and starts sinking.

[@anmolgupta-bj5ce]

Fluid mechanics + applied mechanics = fun with science 🔥🔥🙏🙏

[@abhyuday1294]

Only channel on KZbin, which have new and absolutely amazing science content in each video! Not a single video feels like, ah it's a common sense, always blows my mind! Thank you action lab! ❤️

[@tbjas]

So in the tall beaker it doesn't really seem like it's touching walls. My first thought was friction but it seemed to obvious. And what about that experiment where you make a floater with just enough weight attached so it barely floats, fill a 2L bottle to the brim with water, put your floater inside and screw on the cap. Then if you squeeze the bottle the floater sinks. Release the pressure and it floats again. How does that work...