Thanks for the quick demo. Helped confirm that I had done a problem correctly... or at least that on the right track.

Best demonstration on rotation inertia

Perfect....i m sure niw that I'll never hv doubt on this point ever. Thanks very much sir 🤗🙏

Best demo and explanation. Thank you

Excellent demo. You clear our doubts on moment of inertia and show its effect in real practical life☺️

@msislam6751

2 ай бұрын

Yes. Our sirs do not show this & that's why I was slowly losing my interest in physics.

Thankyou very much indeed. Very good presentation

Moment of inertia for the ring is MR^2 and that of the disc is MR^2/2, since the disc has lesser moment of inertia comparatively in lamen terms it is easier to rotate the disc rather than a ring

Very very thanks sir I was thinking about this practical

Very good video.

Thank you!

TYSM cleared my doubt

Hello I was wondering if you could help me with a unique flywheel calculation please? If I had a way of magnetically supporting a huge flywheel like the aluminum disk one illustrated in your video. Lets say 50 meters in diameter. Is it possible to spin that flywheel with an outside rim speed of 1600 km per hour?

Thanks Sir for this experiment 🙂🙏

thanks king this really helped me understand this topic.

Aluminium is hollow with bigger air resistance plus aluminium have low density, you compare table tennis ball with solid steel ball race. Moment of inertia is about rotation about axis you motor sniping that moment of inertia, feather and steel ball in vacuum shows that gravity accelerates all objects equally if you not count resistance.

@MrAndrius12

5 жыл бұрын

Tennis ball and solid steel ball do not have the same mass. His point was to show two objects of the *same mass* but *different inertia*. Both objects with the same mass will have the same gravitational pull, therefore the force used for this test is the same for both objects, which us fair. As far as density goes, I would not say that would is dense either. Just look at both objects, one is hollow with just the outer layer being the same mass as the *entire solid wooden cylinder*.

Thank u so much

Great, im getting lightweight wheels with 17inch rather than 18inch diameter. Thanks

thank you so much ... perfect :)

Thanks a lot

Which one would be harder to push up a hill? I am going to go with the aluminum ring since all the weight is at the rim. I would generate more “torque” pushing against the solid wood wheel because the center of mass is closer to the center, correct? It’s a bit confusing because you would THINK the wheel that rolls slower DOWN the hill would be the one that is easier to push back up the hill. Correct me if I am wrong please.

Tysm ❤️❤️

Hello! I was wondering if you understood the cause of the rotational inertia? Your demonstration of the effect is good. But the children need to understand the cause.... I would be interested to hear your explanation. Thank You!

@ultimateman1234

5 жыл бұрын

I think I might be able to explain it a bit. Rotational inertia is related to torque. If you imagine a very dense point mass (a ball) on the end of a light rod rotating in a horizontal circle, you understand that the inertia of the ball is related to it's high mass. Now imagine that same rod without the mass on the end and this time you apply a force to the rod. The longer the rod is, the easier it will be for you to cause the rod to rotate, because of the nature of leverage and torque. Replace your force now with the mass, and since the mass tends to maintain its state of motion, it will likewise tend to cause a rotation about the axis in a manner proportional to the length of the rod (or more precisely, the length of the rod squared.) To rephrase, the rotational inertia of a mass depends on distance for the same reason that torque depends on distance: the concept of leverage. If you next ask WHY torque increases with leverage, well, I suppose that's another discussion entirely (related to work, the product of force and distance, which relates to energy.)

Thanks Sir

How can this be applied to choosing rims for fuel economy? If you go with lighter, the overall wheel is lighter but a larger portion of the mass is in the tire.

@vlenhoff

2 жыл бұрын

It would still help. The Rotating mass will be reduced. Handling will improve, and the engine will waste less energy moving heavy wheels.

Thnxs able to solve my question

thanks man

thanks

Formula for velocity of rolling object in incline plane under gravitational force is v=(4/3gh)^1/2 (which you can get from conversation of energy) which is independent of masses! So they should roll at the same rate of we neglect friction and drag force!!

@Mrwiseguy101690

5 жыл бұрын

What do you mean? I'm assuming your formula is for linear velocity, but you're saying they should also roll at the same rate implying angular velocity. One of those statements must be false.

@ameerhamza4816

5 жыл бұрын

@@Mrwiseguy101690 When something is rolling the motion of it's center of mass is translational. This formula is for the motion of center of mass

@Mrwiseguy101690

5 жыл бұрын

@@ameerhamza4816 Yeah, but they wouldn't roll (rotate) at the same rate assuming no slipping. Maybe it was just a misunderstanding on my part.

@ameerhamza4816

5 жыл бұрын

@@Mrwiseguy101690 i think they should! What keep them not rolling at the same speed? Galileo proved his theory of free fall by rolling ball which he explain in his book (Two New Sciences, page 178:)...

@Mrwiseguy101690

5 жыл бұрын

@@ameerhamza4816 Your formula is independent of radius. A large ball and a small ball will have the same linear velocity at the bottom of the ramp, but the smaller ball will have a greater angular velocity.

Anyway, the idea was on the way.. but now I'm thinking about half the disc how will you study the best form.. and also withstand the shock

I always thought the greater the rotational inertia the faster the object spins, but turns out it was the other side.

@kosskrit

3 жыл бұрын

F = m*a where "F" is force (N), "m" is mass (kg) and "a" is acceleration therefore a=F/m so acceleration is inversly proportional to mass. Similar formula applies for Moment (M), angular acceleration (alfa) and inertia (I): M = I*alfa ,but this formula only works in plane (no gyroscopic effects)

@violent_bebop9687

Ай бұрын

The opposite

then why we are not using in car to roll faster it will save battery

mgh = 0.5*I*ω² So large M.I. means low angular velocity hence slow. For formula nerds, I'm talking to you, fellow engineers.

is the mass of both the object taken here is same?

Nice. But, if the acceleration due to gravity is independent of mass (the feather-coin experiment), why is it that the disc rolls down faster than the ring? Am I missing something?

@BTI9115

8 жыл бұрын

+Raghu Seshadri they're not free falling

@okiwill3613

7 жыл бұрын

They definitely are free falling. That was the realization that led to Galileo's magnum opus. An incline is slowed down free fall. The difference has to do with the differences between rotational and translational kinetic energy. All of the ring's mass is away from the center, that is a lot of rotational kinetic energy taking away from translation.

@minhtri2398

7 жыл бұрын

it has been a year since you posted your cmt, I'm not sure you have known the answer or not but I would like to explain. As the author said, the ring has higher moment of inertia since most of it mass distribute far from the rotational center. Thus, this resist angular acceleration (a_a) and makes the ring roll slower. Back to what you said that GRAVITATIONAL acceleration is independent of mass, so muss the ring and the disc reach the the destination at the same time? Well yes, if they are slipping, not rolling so they can have same translational acceleration (a_t). But since they are rolling, a_t depends on a_a in the following formula a_t=R*a_a then the disc translational acceleration is greater so it rolls faster.

@gondalijaz4250

7 жыл бұрын

Minh Tri NGUYEN can you plz explain me in simple words why ring has more moment of inertia tha disc ??

@aanon8849

6 жыл бұрын

its because of how its mass is distributed it is harder to move mass the further away it is from a pivot point (you can try this yourself by grabbing a ruler and putting a weight on it; the further down the ruler away from your hand, the harder it should be to hold up) a cylinder has its mass spread out (some close to the pivot some farther out), but a hoop has all of its mass all the way out at the radius so it takes more to get the mass of the hoop moving

What is your name teacher?

So what happen if you had a solid disk of aluminum with the same size as the ring?

@bh-rf9dd

4 жыл бұрын

It depends. You would definitely have a greater amount of mass for the solid aluminum cylinder. However, the mass will be evenly distributed throughout the axis of rotation. Based on the equations of inertia for a solid and ring cylinder, you would need the solid cylinder with identical radius to have at least 2 times the mass of the cylinder in order to have the same inertia. If the mass of the solid cylinder is greater than 2 times the mass of the ring cylinder then the solid cylinder would have a greater inertia and therefore have a slower rotational velocity at any given time.

@glowiever

3 жыл бұрын

then its mass will be greater, and so its rotational inertia

Suppose the disk and the ring are of the same mass and radius. Which one has the greater moment of inertia?

@michelle.88

4 жыл бұрын

This demo follows that criteria

@kurumi394

4 жыл бұрын

the ring

لازم يكونن بنفس الكتله يا نيوتن تبع الاجانب ليكون القصور للمصمت اقل لان الكتله عاملاساسي بالموضوع وشكرا ينيوتن فرصه حلوه اني اكلمك

Ok, so I should replace my car's aluminium wheels with solid wood wheels to make it faster?

Like the vdo so that such explanation could come to us

So many people in this comment section do not understand the difference between a sliding object and a rolling object, this is just sad

Doesn't it violate that all bodies fall at the same rate of equal density

@albertocabana4362

2 жыл бұрын

No. They start with the same gravitational potential energy, but the ring converts more of its energy into rotational energy than the solid wood due to its larger moment of inertia (since rotational energy is also a thing). Since the wood disk has a smaller moment of inertia, and energy is conserved, more kinetic translational energy is available to the wooden disk than the hollow ring. More kinetic energy available to the wooden disk means a higher velocity, hence why the wooden disk won the race. The same amount of energy and gravitational acceleration exists, but the hollow ring uses more of its energy into rotational motion, which doesn’t help it translate down the ramp

In other words if he shaves weight out of the inside of that disc to equal the weight of the aluminum ring. It would be pretty thin.

After 10 year of this vedio form India

will they behave the same in vacuum. has this been tried in a vacuum. somehow I feel that air might be slowing down the ring.

@dfa9840

7 жыл бұрын

Nandagopal Iyengar The wheel is faster than the ring because of angular momentum. Higher Inertia leads to slower angular velocity, which means that an object rotates slower. As the wheel has a lower inertia it spins faster. Because angular momentum is also conserved in a vacuum ( the earth for example is still spinning) this would change nothing. Regarding air resistance, this proportional to an object's area of resistance, shape, air pressure and the object's velocity squared. Everything except the velocity is the same with both weel and ring. But due to it's higher velocity the weel is actually slowed down more than the ring. So in conclusion: Doing the experiment in a vacuum wouldn't make a difference, it would even make the weel go even faster.

@ameerhamza4816

5 жыл бұрын

@@dfa9840 no actually Galileo show object fall at the same rate regardless of masses by rolling!!!!!

@imadmorsli2871

5 жыл бұрын

its not the masses it is how the masses are distributed which can increase or decrease rotational inertia making an object roll faster for less time or slower for more time. check out mark robers video on how to make the perfect mousetrap car. he explains briefly about rotational inertia and his explanation should give you enough background knowledge to understand. also it is rolling slower because of rotational inertia not air resistance.

@ultimateman1234

5 жыл бұрын

You are incorrect.

Now make the hollow ring of light weight plastic and same size.

@omniyambot9876

4 жыл бұрын

hoting will change

2:04

Still have to show people this vid when trying to explain to peeps

im here after 11 years wow

This is actually incorrect information in the video. The time for which the aluminum disc ,sped up by the motor, takes to slow down is not due to nor is dependent on its rotational inertia. It is effectively due to its speed at the time that you shut off the motor. There is a constant impulse acting on the aluminum disc due to or caused by friction for an amount of time to slow it down at a constant rate and bring it to a stop. Impulse x time = m∆v This is actually for linear motion, but the same concept applies to rotational motion. impulse is not actually force x time, but rather it is force/time. The correct way to interpret this is that the greater the amount of time for which the constant impulse acts the greater the change in velocity. However, you can see that a greater speed effectively increases the amount of time for which a given impulse is acting. There apparently and evidently is a small constant impulse acting on the disc due to friction which is why it takes a long time to bring it to a stop. There is no point in showing the aluminum disc being sped up by the motor to a certain speed also unless it is compared to the same aluminum disc being sped up to a different speed. In this case, the impulse on the disc due to friction is the same and the time it takes to come to a stop would be different due to different speeds as shown by the equation. There are other factors to consider in the other part or example using the inclined plane that are relevant and which are different. You have friction that is different between the two discs and you also have frictional impulse or impulse of friction which is different between the two discs. friction = μ x surface area frictional impulse = μ x support impulse(N) N = mg The friction or surface resistance on the discs would be different due to different coefficents of friction if the surface areas or contact areas are the same. The frictional impulse or impulse of friction acting on each disc opposite its direction of motion would be different due to a difference in the coefficient of friction and also due to a difference in the support impulse presuming that the masses are different. Either the wooden disc would roll down the incline more quickly or the aluminum ring would roll down the incline more slowly due to these other factors being different. The support impulse or impulse of support is what you would incorrectly refer to as the normal force. It would actually be the normal impulse. The normal impulse is numerically equal to the gravitational impulse(i.e. mg) or impulse of gravity for a level surface as shown above. This also means that the gravitational impulse is what you would incorrectly refer to as the gravitational force.

Go cheese! Go cheese! Cheese always wins.

I'm just here because I like spinning things

Nothing matters, only the velocity does. The mass and material doesn't really affect the velocity. It is due to the hallow or solid of the cylinder/ring.

air resistance causes the ring to fall slower. in a vacuum both masses would fall equally fast if they had the same mass.

@BlueEyes-WhiteDrag0n

6 жыл бұрын

Are you Sherlock ?

@ameerhamza4816

5 жыл бұрын

Air resistance and friction combine both things have different coefficient of friction

@ultimateman1234

5 жыл бұрын

Incorrect. Friction at the point of contact with the ramp causes a net torque which creates a rotation. The resistance to that torque is the rotational inertias, which explains why the objects rotate at a different rate. Since they roll without slipping, whichever object has the higher angular acceleration will also have both a higher angular and linear velocity and win the race. Air resistance has nothing to do with it at all.