The Basics of Circular Motion (and Beyond)!

[@AllThingsPhysicsYouTube]

Apologies, but there is a rather large blunder here at 18:15. A conical pendulum has the same period as a simple pendulum ONLY in the small angle regime! I knew that, but somehow still made this misstatement. It's terribly frustrating to have published the video with this mistake. It looks like KZbin will let me cut out the portion of the video where I make this statement, and I'm tempted to do so. Let me know if you think it's fine to leave it as is, with the correction noted, or if I should go ahead and cut out the offending sentence.

[@AKU666]

Cool pfp.

[@KaiseruSoze]

if you fixed it, some ppl would think you're spamming. If you don't others will point out your mistake, over and over. If you do fix it you could repost it as a "second edition" with an explanation for the edit and a new poster image with text something like "The Best Laid Plans of Mice and Men..." .. or ask the "Oracle" chatGPT :) ... so I did that and .... let's say I posted a youtube video containing a mistake and then reposted a fixed video. I want to be clear that it was an honest mistake. What options do I have? ChatGPT said: ChatGPT You have several options to clarify that the original mistake was honest and ensure your audience understands the situation. Here are a few strategies: 1. Post a Comment on the Original Video Pin a comment explaining the mistake and linking to the new, corrected video. Example: “Hey everyone, I made an honest mistake in this video. I’ve uploaded a corrected version here [link]. Apologies for any confusion!” 2. Edit the Video Description Add a note in the description of the original video explaining the mistake and linking to the fixed version. Example: “IMPORTANT: There was an error in this video. Please check out the corrected version here: [link]. It was an honest mistake, and I appreciate your understanding.” 3. Include a Note in the New Video At the beginning of the fixed video, include a brief message acknowledging the mistake and providing context. Be transparent about it. Example: “In the previous version of this video, I made a mistake. This version has the correct information. Thank you for your understanding!” 4. Make a Community Post (if eligible) Use the KZbin community tab (if your channel has access) to make a post explaining the situation and directing viewers to the corrected video. Example: “I want to clarify that I made an honest mistake in my last upload. I’ve re-uploaded a corrected version here [link]. Thank you for your support!” 5. Respond to Comments If viewers comment on the original mistake, respond to them with a short explanation that it was an honest mistake and direct them to the updated video. 6. Create a Short Apology/Explanation Video Post a short video specifically explaining the mistake, clarifying that it was honest, and linking to the corrected version. This is especially effective if the mistake could cause confusion or misunderstanding. 7. Update Video Titles Add "(Original)" or "(Mistake)" to the title of the first video and "(Corrected)" or "(Updated)" to the fixed video title, so viewers immediately know which one to watch. These approaches help maintain transparency and trust with your audience while ensuring they understand that the error was unintentional. You said: any suggestions for the poster image? ChatGPT said: ChatGPT For the poster image (thumbnail) of the corrected video, you'll want to make it visually clear that it's the updated version. Here are a few suggestions: 1. Add a Bold “Corrected” or “Updated” Label Use a noticeable banner or stamp that says “Corrected” or “Updated” in bold letters. Place it in a corner but make sure it's visible. This immediately signals to viewers that the video contains the correct information. 2. Highlight the Error and Correction Consider a split-image thumbnail where one half represents the mistake (e.g., red “X” or text saying “Mistake”) and the other half represents the correction (e.g., green checkmark with “Fixed” or “Corrected”). This visually shows the transition from wrong to right in a simple way. 3. Use an Apology Theme You could include yourself in the thumbnail making a gesture like a thumbs up or apologetic face (if appropriate for your brand). You could add text like "Fixed it!" or "Oops! Now Corrected!" for a friendly tone. 4. Keep it Simple Sometimes simplicity is effective. A clean, bold title that reads “Mistake Fixed!” on a colored background could work well. It quickly conveys the message without too much clutter. 5. Include Visual Cues of the Topic If your video is about a specific topic, keep relevant imagery in the thumbnail, but layer in something that symbolizes the fix, like a pencil erasing a mistake, or a wrench to signify a fix, over the original image. 6. Change Background Color Slightly altering the background color from the original video thumbnail to visually distinguish the new version can help avoid confusion between the two versions. The key is to make sure the thumbnail clearly communicates that this video is the corrected version, ideally in a positive and friendly way that builds trust with your audience.

[@mikip3242]

I prefer it cutted out, you are still on time to gain the views you deserve

[@JohnLRice]

Hey Dave, there are some things you can do in the KZbin Editor. One is called "Corrections" This guy's video explains it kzbin.info/www/bejne/rqqbZKOHaKd_qKM I think you can also throw up a "card" where needed, not just at the end of the video, but I just tried it and it didn't seem to work.

[@AllThingsPhysicsYouTube]

@@JohnLRice I put up a "correction," which causes a flag/card to appear just before I make the incorrect statement. Hopefully, that will help prevent an onslaught of negative comments that I don't know what I'm talking about!

[@SaeedNeamati]

The quality of your videos is amazing. The amount of work you put into your videos shows your passion. Thank you so much.

[@AllThingsPhysicsYouTube]

Thank you for the kind words!

[@WoolyCow]

OH MY GOODNESS HE HAS RETURNED!! This is the greatest sequel of all time...

[@AllThingsPhysicsYouTube]

Heh…thanks! I will try not to disappear for so long next time!

[@kevinlaws7259]

Ignore the clickbait comments - clickbait is only clickbait if you don’t deliver on the headline! You did, and then some. I never knew what I didn’t know about very basic physics until your videos. Great stuff!

[@AllThingsPhysicsYouTube]

Hey, Kevin! I appreciate the comment!

[@yveseduardo]

I used the content of your last video to create an exam question. Nice to see a sequel. This is a great channel

[@AllThingsPhysicsYouTube]

Nice! Glad to see you return. Hopefully, you won't have to wait so long until the next video!

[@LeonBS_Brawling]

soooooo underrated, i like physics :) i want to grow up to be like you

[@AllThingsPhysicsYouTube]

Glad you like the channel! Please help spread the word. And don’t grow up to be like me, you can do better than that. Grow up to be like you!

[@unvergebeneid]

It's interesting to me that so many people perceived the other video as "clickbait" and a "trick question." With my degree in armchair psychology, I would suspect that many of these people have a core believe that they are always the smartest person in the room and therefore cannot possibly give the wrong answer to such a "simple" question. Instead of going "oh, I hadn't seen the problem from this angle" or "I guess it's easy to make wrong assumptions", they lash out to resolve their cognitive dissonance.

[@Eianex]

Not always, it was in the title: 'circular motion', those words. All viewers before entering the video are guided into thinking about 'circular motion'. If there is an element (string being attached to a ball) than behaves in a non-predicted way, in a non 'circular' way... Then why not to call the video: "surprising effect when a circular motion combines with non circular motion" ? That would be the precise title which would guide viewers into the correct mindset from the start. And one of the ways you could define clickbait is: misguide viewers with a title/miniature into making them think that the video is about one thing, when in reality is about other. So at least under this interpretation the term 'clickbait' is indeed correctly used here. Obviously the work done with the slicky and the flexible cords provides usefull insights about how the combined system works. But not about pure circular motion - like the title indicates.

[@unvergebeneid]

@@Eianex yeah well, I don't think KZbinrs have any obligation to make their video titles as clumsy and non-catchy as possible and contain a three-line summary of the entire video, just to avoid being accused of clickbait. But hey, agree to disagree.

[@coreC..]

yeah! A new video. Explained so well. Great visual examples. I especially like the animation @18:46. A sine and a cosine pendulum and the yellow result of it, with a constant speed. How you simplify the formula @13:33 in-place, is also good for viewers: Not adding more lines to read on screen, but only swap things. It makes it look extra fancy, and more easy to follow. It's just one small equation, but still ;) You are a good teacher.

[@AllThingsPhysicsYouTube]

Thanks for the kind words!

[@PhysicsManetta]

Another great video! My AP Physics C students enjoyed this one! They all now hate the term centripetal force! 🤯

[@AllThingsPhysicsYouTube]

Glad you enjoyed it! I’m working on a new video that I think will really impress them. Stay tuned!

[@Henriiyy]

Your video is a very good and careful treatment of rotational movement. I liked it a lot! I've always been annoyed by "it's called centripetal not centrifugal"-people, that don't think carefully. From my point of view I'm excerting a centripetal force on the string, pulling the ball inward. From the balls perspective in its corotating system, it is excerting a centrifugal force, tensioning the string.

[@AllThingsPhysicsYouTube]

Yep, centrifugal force gets a bad rap in my opinion. It’s a perfectly useful concept and is, for all intents and purposes, a very real force if you’re in a rotating frame (which we are).

[@wissahdahmastah]

Great video! I always thought the "centripedal force" was something fishy, thank you for confirming my suspicions!

[@AllThingsPhysicsYouTube]

Be careful…centripetal just means “center seeking,” so it’s certainly possible to have a centripetal force. My issue with it is that students tend to think there must be a single, “centripetal force” whenever there is uniform circular motion, which is not the case.

[@Henriiyy]

​@@AllThingsPhysicsKZbin I guess this is mostly a paedagogical point then. (Which is important as well!) In the strictly formal sense, the net force in the conical pendulum is perfectly well "a force" in the sense that it's the acceleration of the ball, divided by its mass ;)

[@AllThingsPhysicsYouTube]

@@Henriiyy That correct, and I make that point in the video. It is the net force that is the centripetal force.

[@realcygnus]

That OG vid was indeed one of thE niftiest yet rather simple demos I ever seen TBH. & IMO this is a very interesting follow up as well. My ONLY complaint would be how long we had to wait for more. BTW, NO worries at all since trolls will troll.

[@AllThingsPhysicsYouTube]

Yes, you’ve got every right to complain about the lengthy wait, but I’m bound and determined to improve on that!!

[@5eurosenelsuelo]

Another great video. I wish this material is used and reproduced in lessons with a hands-on approach.

[@Name-ps9fx]

I recently learned that if the Sun disappeared instantly, the Earth would not instantly fly off into space...it takes gravity about 8 minutes to reach us, so that is how much time we'd have before a "Space: 1999" happened. There's gotta be something about quantum theory in this somewhere...gravity being a function of the warping of spacetime, and the rate at which spacetime is un-warped...

[@AllThingsPhysicsYouTube]

Did you see that in the previous video I mentioned that Earth would continue in circular motion for 8 minutes if the Sun were to suddenly disappear?

[@coreC..]

Now that you mention it: If in the previous video the balls were swapped by the sun and the earth, i would have chosen the right answer. Which is strange.. I must have seen more causality videos instead of these hardcore physics videos lately. But if you think about it: If a ball on a slinky does not know the slinky is loose at the other end, then why behave differently? => continue circular path. (causality has not much to do on the little ball's scale, but experiencing no change does).

[@asheshgupta4845]

so gravitons aree faster than photos?

[@coreC..]

@@asheshgupta4845 well.. nothing beats the speed of information, no matter what mediator. So they told me ;)

[@AllThingsPhysicsYouTube]

@@asheshgupta4845same sped, hence the 8 minutes.

[@markpell8979]

I enjoyed this immensely and appreciate your ideas and hard work. I'm sure Dr_LK, who commented below, disagrees with me already on both counts. 😉 Thanks!

[@sonyaraman]

Cool stuff indeed! I just like the bold manner of addressing some viewers claims 😊

[@Aanand-vi9nw]

I was really came there to saw RDJ😂 but this is insannnnnnnn...😎

[@realroadrunnr]

I only unterstand half of it, maybe even less. But it is interesting nonetheless and you’re doing a good job with these videos. I’m looking forward to your next videos :)

[@AllThingsPhysicsYouTube]

Thanks! 😃

[@ClockworkAvatar]

I've always found the rotating reference frame interpretation to be the most intuitive.

[@ostanin_vadym]

Thank you for interesting content

[@GodmanchesterGoblin]

Fascinating! In the case of the ball rolling around the cylinder, my brain is wondering whether there are also gyroscopic effects at work. The ball is rolling along in contact with two perpendicular surfaces, so at any instant, its axis of rotation is at 45 degrees to the axis of the cylinder. And what happens when the ball exits the cylinder, since it has angular momentum which is also at 45 degrees to the surface of the table. Maybe nothing happens, but I felt that the video only considered the mass moving around the cylinder and not the fact that it was spinning at 45 degrees. Can that be ignored?

[@AllThingsPhysicsYouTube]

This is a great point, and I've got a future video planned on this exact topic. The gyroscopic effects are definitely present and quite surprising, but they don't change the fact that Newton's second law is still satisfied, so they don't enter into the discussion in this video. Stay tuned!

[@GodmanchesterGoblin]

@@AllThingsPhysicsKZbin Thanks! And greetings from the UK.

[@coreC..]

Indeed. I hadn't thought of that. Cool. Other people's ideas help you think.

[@vincentaime1715]

What sofware do you use to insert your equation in your videos?

[@AllThingsPhysicsYouTube]

I use manim, community edition. This is the software developed by Grant Sanderson of 3Blue1Brown. This is mentioned in the Square Orbit Part 2 video.

[@vincentaime1715]

@@AllThingsPhysicsKZbin 🙏

[@apq3710]

But wait, the period of a simple pendulum isn't the same as the period of a conic pendulum. The latter can be expressed in terms of elementary functions while the former cannot. This trick with decomposing 2d motion into 2 oscillations works well with springs but I'm not so sure about simple pendulums. Nice video btw, I enjoy your content!

[@AllThingsPhysicsYouTube]

Yes, of course you are correct. I misstated that in the video. Sigh...you work so hard to make something like this and then screw up by letting something little slip in. I forgot that everything I was doing was in the small angle approximation. Doh! Darn it, now I have to figure out how to correct this without re-uploading an entirely new video.

[@OneEyedJacker]

In your ball rolling inside the ring analogy to the ball on a string you do not account for the rotational inertia of the rolling ball. Might this have an effect on the path?

[@KaiseruSoze]

OTOH, hypotenuse, base and opposite sides work well when discussing trig. I.e., well defined labels help us communicate. But, yeah "centripetal force" can be confusing. Your explanation, however, made it clear what the phrase refers to. And more importantly, the context where we can use "centripetal force".

[@RobiulHasan-t1l]

In which direction does the radius vector act, from the center of the circle to the circumference or from the circumference to the center of the circle?

[@Sugar3Glider]

Curious: if I have a sphere traveling through space with another much heavier sphere inside of it, could I alter the trajectory of them by adjusting the location of the heavier sphere? i.e. heavy ball spin around really fast only to be "caught" by an electromagnet to "jump" the whole device.

[@RobiulHasan-t1l]

What is the total acceleration acting on an object as it moves in a circular path? Like centripetal acceleration, tangential to change in velocity, angular acceleration to change in angular velocity. How did the forces work for all these accelerations? How do all the balls move the object?

[@asheshgupta4845]

great lecture sir btw can u make a video on centre of mass or recommend me something as i have difficulty understand it

[@crystaldbj]

Conical pendulum is just an infinite number of plane pendulums, sort of? Very cool.

[@DandoPorsaco-ho1zs]

You might not like the term "centripetal force", but "net/result centripetal force" is fine, as is "centripetal component of a force".

[@AllThingsPhysicsYouTube]

This is true. The problem is that when there is only a single force, then the net force is equal to that single force, which students then associate with “the centripetal force”. Case in point, the tension force when a ball is being swung around on a string is seen as “the centripetal force”, even though it might not point towards the center of the circle.

[@JohnLRice]

Fascinating and well done video, Dave! Excellent and practical idea of using the cylinder with the notch to eliminate any slight effect from the string or spring still being attached to the ball when released. 👍👍The word "osculate" made me laugh as it sounds like how Popeye would pronounce "oscillate"? "Holds still Bluto whiles I osculates yer face with my fists!" 😅 I'd be interested in seeing more discussion and practical experiments with a rotating string never becoming perfectly horizontal no matter how fast it is spun, as this seems unintuitive to me and seems like with a fast enough motor and strong enough string/cable that it might be achieved? Maybe there is some combination of factors like rotation speed, size of the weight at the end of the string, string stiffness, and string length, along with Earth's gravity where a perfectly horizontal plane of motion can be achieved? (and the formula would scale up or down properly for different gravities, like the Earth vs the Moon vs Neptune etc.?) Or is it that it just seems like it does and would be good enough for most practical purposes but there will always the slightest bit of sag? I know you may have explained this with the formulas but that is way over my head! (I'm just a dumb drummer after all!🤭) I'm thinking if you removed the guard from a weed eater, held it parallel to the ground and then fired a laser across the string and compared it to the same experiment with the weed eater held perpendicular to the ground if you could measure any difference, or would the motion of the weed eater mechanism not be precise enough and the string be too short for any available measuring instruments to measure the deviation difference? Keep up the good work on your videos!

[@alanmon2690]

@JohnRice forgive me if I'm talking nonsense, it's been 55 years since I've had to worry about these things, but isn't it analogous to the catenary problem where the chain remains curved despite the horizontal force because the horizontal force needed to remove that infinitesimally small dip caused by gravity becomes infinitively large? If I were to be nit-picky, the rotating string is not actually a straight, rigid rod, it is probably slightly bowed because it is dragging the ball (moving the direction of the vector away from the centre) and thus slightly shorter...

[@AllThingsPhysicsYouTube]

Hi John! The issue is that gravity always pulls down on the ball, so there must be an upward force to counter balance it, and this must come from the string. If the string were perfectly horizontal then there would be no upward component to counteract gravity. But your intuition is correct that you can get VERY close to horizontal by spinning it faster and faster, but in order to get perfectly horizontal would require an infinitely fast spin rate, which is not possible of course.

[@JohnLRice]

@@alanmon2690 Sounds right to me? I'm more likely to talk nonsense than any one here, because while I think I'm fairly creative and inventive, I seriously lack the math skills and scientific knowledge so I tend to go down the rabbit hole of my own imaginings! 😅

[@JohnLRice]

@@AllThingsPhysicsKZbin Thanks Dave! My mind keeps going through "but what if" scenarios and then refuting them . . .but then again what if . . .? 😅🤦‍♂ I kind wish I lived near where you teach so I could take your classes, or at least audit them because I lack the math skills to be accepted as a student!

[@tanushiii8552]

could you please do an explanation on gravitation and orbital mechanics 🙏

[@OneEyedJacker]

If the slinky was constrained to remain straight the path would be that of the center of mass of the system which would move closer to the ball as the spring contracted. Since the system would rotate clockwise if the original rotation was clockwise, I believe the center of mass would move tangentially but the ball would move in a cycloidal path around the moving center of mass.

[@vijaykag1144]

@AllThingsPhysicsKZbin There is no constrain as such for minimal angle, the calculation shown during 16:50 is incorrect. The correct angle θ = arc tan( w^2 l/g). Also when angular velocity matches with natural frequency (w = w_c) the angle will be π/4, which is not there in your experimental results 19:20. Kindly correct in your video!

[@Dismythed]

The osculating momentum comes from when the ball disconnects, it is as if it is pointing toward the center of the circle as it moves. But instead of rotating, it moves forward. It is identical to the pendulum because the rotation is what is resisting the gravity. The gravity creates the pendulum and the rotation resists it in equal measure, which is what causes the cone height difference.

[@RGD2k]

Great stuff! Agree with proposal Re 'net' over 'centripetal'. Similar confusion comes up for motion of charged particles in E and B fields, although it's worse there because of improper handling of total / material derivative vs partial derivative: These are equal only if nothing is moving, neither the test charge upon which the fields are assumed to be acting, nor the source net charges forming the E field, nor the source J elements forming the B field. This is why one needs to jump back and forth between newtonian mechanics with masses and net accelerations, and electrodynamics with fields, charge spatial scalar net density source field, and current spatial vector net source fields, along with a 'hack' not actually part of the equation set to determine the effective net force from the B field field contribution. When you get it correct, you realise that inductance is itself a form of inertia, and the the typical form of what are called Maxwell's Equations of Electrodynamics (M-E) are only an approximation particularly valid and useful for cases where nothing is substantially in motion, or moving at relevant timescales to the oscilations under consideration (i.e., not particularly brilliant particle accelerators for which the former case holds, and antenna considerably stationary (i.e. not mechanically oscillating at frequencies similar to the oscillation frequency of the currents). Amongst other things, this is why electric motor/actuator design still relies not upon M-E, but Faraday / Ampere's laws, which are correct for moving things as the total derivative is included. Simply pick up any engineering textbook on such mechanisms and it will become obvious: M-E is only valid for antenna! What I find interesting is that charge itself appears to be a trivector quantity. It has 'two signs' which are obviously in opposition to each other, and what matters is that Gauss' law (in integral form) is obeyed: Just as should be expected for a trivector quantity. Yet, the source of a magnetic field certainly appears to be a bivector quantity, given that 4pi steradians of orientation are available in 3d space, and there indeed exist no magnetic monopoles - each 'pole' being just the backside of the other! Bivectors are oriented-area-magnitude quantities (for which the quantity is an oriented surface, for which the specific shape of the contour defining the edge is not important) trivectors are oriented-volume-magnitude quantities (for which, again, the specific shape of the surface defining it is not important), whereas vectors are just oriented-distance-quantities. The distinction comes from Geometric Algebra. To get the cross vector product from a bivector quantity, you just multiply it by the imaginary identity i (which squares to minus one): effectively asking for 'what is at right angles to this'. Interestingly, no information is lost doing this, except in that you lose knowledge of the proper dimension of the quantity. Note that not everything is or should be reduced to a vector quantity! Else we would not need 'covectors' for some things... In general, when doing dimensional analysis, you should never cancel distances which are fundamentally defined to be measured at right angles to each other, at least not without introducing a factor i in the units to keep track... This is what distinguishes 'shear rate' (distance units defined at right-angles: m/s along divided by m across, therefore a bivector quantity, often unit-cancelled improperly to just 'per second') from 'frequency': Also units 'per second' but not a spatial quantity, but the inverse of the period of something repeating. These two measures are clearly NOT equivalent! And this mistake typically invalidates a lot of what would be otherwise simple dimensional analysis. And this is why you need to understand Geometric Analysis, at least as far as the distinction between vectors, bivectors, trivectors and higher. Also note what has only two possible magnitudes, albeit this time on a 2d-plane? Rotation. Because bivector is as high as you can go in a 2d space. It's either counterclockwise or clockwise, just like how charges can be only positive or negative, and nothing in between. But also further: In 2d space, rotation must be conserved! There is literally no space to allow 'flipping over' an object with rotation to allow it to orient the other way. What does this imply about charge? Perhaps this is the source of conservation of charge: As a trivector quantity in a 3d space, net charge has to be conserved because there isn't a way to rotate it between orientations without access to a higher dimension. Consider also that both rotational and linear momentum can be converted into only rotation at a higher dimensional space: Projective Geometric Algebra uses this one trick to convert matrices of the form Y=Mx+B to the more useful form Y=Mx: All you do is add an extra dimension, and define an 'origin' point in it, to handle all spatial displacement vectors (of objects constrained to be in the subspace) by having their location vectors instead represented by the intersection of a higher-dimensional line passing through the lower-dimensional space, and that origin point. If all objects in the subspace are treated this way, then one obtains the simpler matrices without any loss of information. All displacements just become a kind of rotation, and this works even for the subspace being 3d, because GA allows dealing with spaces of arbitrary dimension! And when you do this, you still have conservation of both linear and rotational momentum, both of those happen within the same calculation. Anyway, as relates the previous video: Of course mechanical information only moves at the speed of sound in a medium! The ball can't 'know' about the event of the release of the other end until the 'sound' arrives down the tension element which was applying the force! What gets interesting is that there are often separate 'speeds of sound' depending on which orientation the sound has within the solid medium... Shear waves vs compression waves, for instance.

[@HisHigherness8472]

New Sub 🕶️👍

[@AllThingsPhysicsYouTube]

Awesome! Please consider sharing with others who would enjoy it!

[@gustavocortico1681]

Should you add the amount traveled due to the speed of sound in the rope? The centripetal force wouldn't have time to change.

[@maths.visualization]

Can you share video code?

[@kenhoffman5363]

Seems the centripetal normal force is not the only acting force in the plastic cylinder. When you first accelerated the ball inside the cylinder you were applying a normal force which immediately encountered Newton's 3rd law at the wall of the cylinder. Where the wall was cut out and the normal centripetal was removed the ball returned to the original interrupted horizontal force direction.

[@mrzenox9835]

Anyone here thought the thumbnail had Bill Cifer?

[@AllThingsPhysicsYouTube]

If you look through the comments you’ll see that at least two others did. 😂

[@mrzenox9835]

@@AllThingsPhysicsKZbin great minds think alike :D

[@sp.v.207]

this is the oposite of clickbait

[@coreC..]

People that called the previous video clickbait hadn't even watched the complete video, i guess. Maybe he thought he searched for "Physical" but pressed ENTER too quickly, and landed on a real experimental "Physics" channel by his accident?

[@paradiselost9946]

off topic yet on topic... flywheels... and forces applied to them... am i correct in believing that as constant rotational velocity is also a constant angular acceleration of mass, change of inertia, that it takes power to simply maintain constant rotational velocity, ignoring friction? this is something i have never seen anyone deal with, explain, outline... its related to all this hyped up BS (imho) about "flywheel storage"... as far as i understand it, simply rotating a large mass at constant RPM requires energy? from what i can gather, for a given force, you cant simply keep adding " infinite flywheel mass" and store "infinite energy" in that flywheel or rotating mass, somewhere there is a limit to the mass one can accelerate from that force... and if you dont apply enough to overcome the change in inertia, it slows down... without removing or "extracting" any in performing "useful work"... if any channel can do a good job of explaining this, its this one...

[@AllThingsPhysicsYouTube]

A constant angular velocity is zero angular acceleration (no change in velocity), so it requires zero torque. So a big wheel can be used to store energy. It takes energy (work) to speed it up, but then it will spin on its own (neglecting friction…). When you want the energy back you mage the wheel do work and it will lose its energy in the process. Actually, this topic could make an interesting video. And yes, there is clearly a limit to the flywheel mass. How it’s related is that a small part of the flywheel mass can be thought of as a mass going around in uniform circular motion, so this mass element is undergoing a centripetal acceleration. Therefore, there is a force acting on the mass element. This is an internal force that ultimately comes from the (internal) intermolecular forces within the material. As the radius (or speed) of the flywheel increases, so do these internal forces, so there will come a point when these internal forces will not be able to supply the necessary forces and the flywheel will rip itself apart.

[@Dismythed]

What I got from that is that you disproved your previous video. At no time did I see you prove that the angle goes off. The ball leaving the cylinder proved that. I have no idea what the conical explanation was supposed to prove since it applies to the downward force of gravity, not a carry-on force of the ball causing its path to drift. Maybe a proper summary would resolve this?

[@AllThingsPhysicsYouTube]

I think you missed the point. The ball leaving the cylinder goes off tangent to the circle because the force instantly disappears. The ball on a string does not leave tangent to the circle because there is a finite time delay due to the tension wave in the string. The conical pendulum was just my attempt to show how to solve the real ball on a string problem more carefully, and to emphasize the confusion that can arise from the term "centripetal force."

[@NicholasWilliams-uk9xu]

(the strong force = centripetal force)

[@coreC..]

'net' over 'centripetal'..

[@TheChaosGoddess1024]

Um why is Bill cipher in the thumbnail? I mean im not complaining

[@AllThingsPhysicsYouTube]

You’re the second person to say something like this, so I finally looked it up, and you’re right, it’s Bill Cipher! I had no idea!

[@oldjoec3710]

In my view, the refusal to recognize centripetal force as a thing leads to an important loss of insight in this case. The force of the string on the ball has two orthogonal components: The vertical component overcomes the natural tendency to accelerate downward under the effect of gravitiy. (I would say the "overcomes the gravitational force", but that would start a whole separate argument, in which Albert E's name would be invoked.) The horizontal component is EXACTLY the centripetal force that you're trying to avoid discussing. IMO, your description complicates and mystifies the motion, rather than explaining it in clearest terms.

[@AllThingsPhysicsYouTube]

But those two orthogonal components come right out of Newton’s second law. There’s no loss of insight, just loss of the term centripetal force. It’s still the horizontal component of tension that leads to the centripetal acceleration. But by avoiding the term centripetal force, students won’t be lulled into thinking that tension is the centripetal force, which they will learn by solving the 2D version of this problem.

[@noj5393]

first!

[@coreC..]

And now try to win as many likes to your comment as possible, and KZbin lets your comment stay visible forever. By far most chance to hit a 'best comment', if you're one the the very first to comment. But many! of those 'best' comments are not at all good :) Does KZbin really set 'comments sorting' to 'best first', even if the publisher manually set it to 'newest first'? ;-)

[@scissorinfo4082]

1 year later

[@AllThingsPhysicsYouTube]

Yeah, I know. I’m working on it!

[@scissorinfo4082]

@@AllThingsPhysicsKZbin Your videos are actually great, This reminds me of veritasium

[@CanuckBeaver]

@CanuckBeaver 58 minutes ago This is absurd. I am a retired physics teacher. You keep saying that Centripetal force is not necessary, or is irrelevant, and cross it out. Centripetal force is the ONLY thing that matters to keep that circular motion happening. The ball moving out of the window in the plastic ring is the correct observation. You then divert into running in mathematical circles and lose track of reality. When swinging the ball on a string, you drew the string vector angle, but that has a pure horizontal Centripetal force component that is 100% physically real, or the ball would not circle. You ignore it. The leather sling was common in ancient history, but according to physics textbooks, once the shepherd boy let go the thong, the rock should just keep rotating in a circle in the air as the boy walks away, affected only by gravity as the circling ball falls to the ground. We always teach the "conservation of angular momentum" with rotating bicycle wheels, but angular momentum is NOT conserved. As teachers we are blind to the centripetal force transferred to the rim through the metal spokes. Wiki's article on the topic has a short phrase, "for rigid bodies" that everyone ignores.-- Skaters rotate faster when they pull their arms in. But that is Not Conserving angular momentum, it is the arm muscles applying centripetal force to the mass of the arms of the rigid body of the skater, and can be tiring to the skater. Matter accreting onto black hole increases in velocity only because of the gravitational centripetal force vector. A nebula cloud without a concentrated central mass would have no reason to accelerate.

[@AllThingsPhysicsYouTube]

Actually, I never said the centripetal force is not necessary or irrelevant. Go watch the video again. (And angular momentum is definitely conserved, assuming there are no external torques acting on the system.)

[@CanuckBeaver]

@@AllThingsPhysicsKZbin 1- You showed centripetal force with a big x through it and repeatedly said to not use it. Look at your own video!!! 2. It is not conserved at all. Otherwise the rock would keep circling with angular momentum. That is so absurd. How do you explain the rock going straight if you insist the rock conserves angular momentum??? Name one example in the every day world (not particle physics) of a rotating object with no physical (rope, metal wheel) or force (gravity, charge).

[@AllThingsPhysicsYouTube]

@@CanuckBeaver Woops...you are correct, I did indeed say it was unnecessary, and I stand by that. You can understand and solve the problem without ever using the term centripetal force.

[@CanuckBeaver]

@@AllThingsPhysicsKZbin Why not talk about reality? Math is killing physics, and I am writing a book on that topic, and Cenntripetal is a big deal. Your method ignores reality of forces, like explaining how to calulate orbits of satellites but ignoring gravity. In your system, F is meaningless mathematical fluff. Have fun with math, but don't ignore reality or your work becomes irrelevant.

[@wayneyadams]

Yes CLICKBAIT! The whole point of the ball and string question is to teach students about inertia and the fact that a body moves with constant velocity in the absence of a net external force as happens once the string tension goes to zero in a time too short for you to capture on video. I am going to ask you one more time for you qualifications and I don't want another meely mouthed avoidance by saying you give your name because I do not see it anywhere in the comments nor on your home channel page. So, who are you, and what are your qualifications?!

[@Dr_LK]

Centripetal force must exist for circular motion. How this force arises depends on the situation, I.e. component of string tension, friction from tyres, reaction force from wall, etc. Have you read physics books? Why you confuse your viewers?

[@mikip3242]

You wrote this comment 16 min after the video was published, so before watching the actual the video (which is 20 min long). The point made in the video is that instead of talking about "the centripetal force" we should be talking about "the centripetal component of the net force". Is a very minor change and I would agree that it is of little importance.

[@Dr_LK]

@@mikip3242 i had seen enough to comment. i have taught thousands of students, and we all understand that whatever resultant force exists, if it is directed towards the center (centripetal) will cause circular motion.

[@AllThingsPhysicsYouTube]

@@Dr_LK You are correct that the resultant force is centripetal. I state this very clearly in the video. But my experience is that most students who are learning about circular motion think of "the centripetal force" as a specific, single force that needs to be added to a free-body diagram. This can be avoided by not ever mentioning "the centripetal force" and instead just discussing the specific forces that are acting on the object.

[@kartikgkalita]

​@@AllThingsPhysicsKZbin still unnecessary. I haven't met a single student that had that problem

[@yveseduardo]

​@@kartikgkalita good for you. I've met a lot