I had class with Professor Peter. Great teacher...so calm....He surrounds physics from every point. I like professors like that ! Very good explanation how static friction can be responsible for creating an alpha on the wheel rotation.

how tf does he just write backwards that fast

@mitocw

6 жыл бұрын

He is writing it forwards, the camera records it backwards, and software (or video equipment) flips the video. See lightboard.info to see how this was done.

@kentoutcourt

4 жыл бұрын

I couldn't concentrate because of that...

@TayoEXE

4 жыл бұрын

I thought that too, then I realized he was doing all of this left-handed. Not that left-handed people can't do that, but there are far fewer left-handed people than right-handed people, so I realized he might have just flipped the video and wore a symmetrical shirt. You can tell since the buttons are normally on the other side. Good way to do it though.

@hanzo52

4 жыл бұрын

@@mitocw Backwards recording camera!

@akashkadambi3732

2 жыл бұрын

It is same like Writing on Mirror and recording Mirror 😂😂😂

Wonderful! Thanks fo r the upload.

You are a great teacher

thanks for such a good explanation since everywhere it was given static friction always come in pure rolling but thats not the case since in normal horizontal surface the velocity of the contact point and the contact surface is same son no friction comes

If we take the center of the wheel as a reference point, so relative to this point the contact point between the wheel and the inclined is in motion (not at rest). My question what is the expression of the work done by the friction between the wheel and incline relative to the center of the wheel?

@renmas00

Жыл бұрын

Work done = Torque times angle of rotation and hence equal to frictional force * radius * angle of rotation

Sorry guys, I'm new to this. If we replaced the circle with a square, and applied the same angular force in this example to the square, why does the square not move as freely as the circle?

@gabrielbialek7895

Жыл бұрын

Hey man, I hope you got your question answered 4 years ago, but if the torque is applied to a square, it would not be the same because it would be slipping. When rolling, the system is not slipping, that’s why it’s static friction exerting a torque. When it’s a square, the force exerted by friction is kenetic, and thus the square would be slipping, no angular acceleration, and everything would be linear and not angular

@anamitradasxia4490

Ай бұрын

The surface at contact is too large for effective rolling due to which it rather slips than executing a rolling motion

Isn't the wheel's contact point with the ground the point about which the wheel is rotating ? If so static friction should not produce any torque on the body right ? What's wrong in my thinking ?

@evanmorgan2086

2 жыл бұрын

The point at which the wheel is rotating about is at a distance of the radius off the ground (the wheel's center) while the contact point is on the ground.

if friction causes torque in case of inclined, then which force causes torque in linear case? Is the the person who throws? because as far as my senses, I have seen people giving initial linear push (force) to objects, no body produces torque before throw at bowling. Please correct me. I am so confused.

What about dynamic friction, along which direction it will act and how it will affect the motion of the rolling object. Please answer me Sir, keeping in view the direction of instantaneous impact of the rolling disc on the surface.

@tysonff2627

Жыл бұрын

The point of contact is in rest...so why would dynamic friction come into picture..?

@idkconflict

10 күн бұрын

@@tysonff2627could you elaborate on that

Is friction a backward or inward pull against a motion in some v direction and depends on the coefficients of friction of surface material?

@abhirupkundu2778

7 ай бұрын

yes, friction depends on the friction coefficient for every body(surface type or material) and it is a backward pull which opposes the direction of linear velocity of every body and supports angular velocity if the body can roll

Sir can we perform this on inclined plane

Isn't the maximum value of static friction not "mu N" Here?

What if the center of mass is not located at the center of the disc?

@abhirupkundu2778

7 ай бұрын

then it depends on where the COM is located, and where the force is being applied on the disc so that it could roll due to the angular velocity and acceleration produced by the torque produced by friction once a force is applied collinearly to the COM. If the force is applied on some other part of the disc which does not coincide with the COM, then the body will roll even faster due to both the force and friction

Can someone explain me this? It says that the slipping wheel has not static friction, well that's right. But still has kinetic friction, right? And the other question is: in the case of the rolling wheel where there is static friction. If the wheel is rotating with zero linear acceleration, does it still has static friction? Or not and it only stops in theory because of air resistance?

@daksheshprasad9941

4 жыл бұрын

your first ques. During pure rolling there is no relative motion between the surfaces of sphere and the floor or ground.So only static friction acts.But during Rolling WITH slipping kinectic friction acts uptill pure rolling doesn't start. 2nd ques.yes if it has no linear accn it still suffers static friction(Remember Friction is the cause of rolling without it the topic doesn't exist because it produces the necessary torque for the body to roll).Hope it helps:)

@lea1822

4 жыл бұрын

@@daksheshprasad9941 Thanks. What I still don't understand is: I supposed that static friction only occurs when there is an acting force (e.g., in the case of gravity in inclined plane). Yet if I imagine an scenario where there is no linear acceleration taking place, what force is the one that generates the static friction then? Or is this "static friction" different from the static friction that takes place in the usual situations in non rolling bodies, and occurs in absence of active forces?

@daksheshprasad9941

4 жыл бұрын

@@lea1822 No motion can start spontaneously in the absence of external force.A wheel or ball on a surface is held there by static friction. In order to start the rolling motion, a force or torque must be applied to the wheel. The force of the static sliding friction prevents the wheel from sliding and thus initiates the rolling motion.

Doubt: (For pure rolling motion on a horizontal surface) if static friction does not act the net torque will also be zero , then how can the body continue the rolling motion ?

@dogac2122

Жыл бұрын

i guess it was rolling at inital otherwise it cannot roll without angular accelaration

I am not getting completely. my ques is that if torque is provided by friction so why the wheel stopped aftr sometime as friction is always there.

@fikrynuhman2944

4 жыл бұрын

jagmohan gautam in reality when an object rolls there is also a normal reaction acting on it. All real objects a compressible, therefore this normal reaction does not act exactly through the center of mass. Instead it acts through a point slightly to the right or left to the center of mass according to the direction of rolling. Torque produced due to this decelerates the object and brings it to rest

@jackhe7859

4 жыл бұрын

friction only acts as long as there is nonzero velocity: if you slide a block down a table, it doe not start to reverse its direction due to friction

Sir. If the static friction on a rolling wheel is zero, what makes it roll??

@its_saam9459

3 жыл бұрын

If there is no friction it will not roll, it will simply slide like an ice puck on a surface.

@edwardmalpartida5894

3 жыл бұрын

Exactly, there’s something off with that “first case”, that object could not be rolling if there was no friction

@ibrahimalmetwale3282

3 жыл бұрын

@@edwardmalpartida5894 Nope! If the wheel was not rolling, then it was will never roll while it is slipping unless there is torque on it. Mainly by static friction. However if it was put in rolling from the beginning it will keep rolling and translating (slipping) independently of each other, meaning that: Vc.m. not necessarily equal to Rw of the wheel. You need friction to start rolling but after that you don't need it. Just like you need some force to start moving but once you move, you can keep so (Newton's first law)

If no friction is present in the first example how does it roll? Wouldn't it just slide?

@mustafatufan2000

3 жыл бұрын

I think It has a constant angular velocity.

@awwadsharaf

3 жыл бұрын

I agree

ty very much sir

Will it also depend on material and inclination angle and also the area?

@GamesOnline211

4 жыл бұрын

Friction does not depend on area, but it does depend on the contact material and the plane inclination . You can see how the inclination dependency comes to play by drawing a force schematics on a problem similar to the one shown in the video , for some angle alpha . The contacy material affects friction since every surface has different friction coefficint (mu) , and static friction follows f

Since its rolling

Hi, it would be very helpful if someone could help me with this question: Let's say we have a wheel, we give it a starting speed (Ucm let's call it) and it rolls on a surface with friction. Now, everyday life observation says the wheel must stop at some point, right? Well, how does it stop? I can't seem to find out a way where the friction's torque does not accelerate one movement and decelerate the other...

@giannisskoun

6 жыл бұрын

Yeah I just saw that he actually explains it, thanks a lot!

@Gigasimo456

5 жыл бұрын

I'm late, also a real wheel isn't perfectly circular and the contact point isn't a point, but rather an ellipse. They both cause the wheel to slow down.

@abhirupkundu2778

7 ай бұрын

its because nothing in real life is perfectly circular. And every point on the wheel is irregular with respect to the surface. Hence, friction is irregular on each part causing different linear accelerations which oppose and support each other.

This topic is very important if you want to study mobile robots.

Why is the static friction zero in first case?

@renmas00

Жыл бұрын

Static friction is resistance to the body at rest against external force trying to move it. Here in the first case, the the body doesn't subjected to any external force and hence no static friction.

sir which software you use? really nice video liked it

Sir,is friction is necessary to establish pure rolling?

@gyurhanaziz7676

6 ай бұрын

yes(if you are talking about a wheel)

what about Dynamic friction, doesn't it also act on the wheel after it starts moving?

@realrakhi

3 жыл бұрын

No

@piyush2404

3 жыл бұрын

That's the whole point no, the bottom point that is in contact with the surface is at instantaneous rest! If that portion is not moving at all then how would you apply Kinetic friction?!

@abadibi

3 жыл бұрын

@@piyush2404 thanks for the explanation!

@piyush2404

3 жыл бұрын

@@abadibi You're welcome buddy, have a nice day🤗

This is kinda weird to me b/c he's facing me but his writing is legible which makes me feel like this is a mirror reflection which makes me feel like he's actually where I am but I'm where I am so he must be me and now I'm having an identity crisis.

Best

if static friction=0 how the wheel rotate?

@shaswatsatyam

3 жыл бұрын

It will rotate at its position.

@user-dj9px1qc1x

2 жыл бұрын

@@shaswatsatyam what are you talking about, it wouldn't rotate then. It would just slide down the hill

@renmas00

Жыл бұрын

Wheel will rotate still as it is moving with uniform velocity. Static friction will be there when there is an external force trying to rotate the wheel at rest. Though the point of contact is stationary, there is no external force and so there is no static friction.

I miss Walter everytime when I see these lectures

@sheharyaar48

5 жыл бұрын

Same here...miss him every time

@ameerhamza4816

5 жыл бұрын

Then go watch him instead of missing! He was not the only one good teacher

@_DVshow_

5 жыл бұрын

Plz show some respect

@jaykay6249

4 жыл бұрын

dev pandey He was a perv

@joshuayang2369

4 жыл бұрын

He did get fired for being a perv search it up

I think there's something wrong with your explanation, Sir.

@awwadsharaf

3 жыл бұрын

I agree

@joniloops

3 жыл бұрын

@@awwadsharaf the fs is a force that is opposite to slipping, hence it should be pointing down the incline, not upwards. The rolling movement will tend to slip relatively to the plane...the wheel surface point of contact will not slip backwards and therefore, rolls, because fs prevents that from happening...or does it?

@Rajendrakumar-qf3om

3 жыл бұрын

Everything is correct

Wtf static friction while rolling???

@antoniomangiapane8922

5 жыл бұрын

The peculiarity of pure rolling is in the fact that the contact point has velocity equal to zero, and for this reason the force exchanged between the wheel and the plane is of static friction.

@Evil_moorthy

5 жыл бұрын

@@antoniomangiapane8922 So you are saying when it's rolling with sliding we should use rolling friction and when it's pure rolling static friction should be used?

@antoniomangiapane8922

5 жыл бұрын

I think he means rolling friction when he says static. When there’s sliding we use dynamic friction.

@Evil_moorthy

5 жыл бұрын

@@antoniomangiapane8922 Yeah he should have meant rolling friction.

Sir if static friction is 0 how the wheel rotate sir

@ericmatos9583

3 жыл бұрын

He says the wheel has an initial velocity (Vcm) for the horizontal case (in a vacuum). Therefore, it will continue to roll if no other forces are acting on the wheel. I hope this clears that up a little bit. Good luck!

How is this video shot!!

Sir can you please do a problem for a wheelchair move up a slope of 5°, with total weight is 150kg

If u write from your side on a transparent thing, to us on this side the words should appear laterally inverted....!!!

@zuboragabora8966

4 жыл бұрын

video is flipped

this 2 people chat XD

Jyst put it in laymen terms In other word's The bloody wheel wants to stay home an eat ice cream.

Is this dude writing backwards?!?

@zuboragabora8966

4 жыл бұрын

video is flipped

@joniloops

3 жыл бұрын

@@zuboragabora8966 or a mirror

@joniloops

3 жыл бұрын

he must be right-handed, however he writes using the left hand...so, the image is horizontally flipped.

Anyone in class 11 🤔

i can clearly say that indians have good education system than americans

@Tylauriente

5 жыл бұрын

Bro, your grammar is trash. I wouldn't be making fun of another education system. Yours has clearly failed you.

@shikharsoni3971

5 жыл бұрын

This is the most stupid and ignorant comment that I have seen in a while.

@srihari8213

5 жыл бұрын

I don't think like that

@pranjalverma3501

5 жыл бұрын

What makes you say that !! while some students excel in their careers in STEM,there are lots of students who are failed and commit sucide.Indians only give respect to STEM subjects which has really destroyed a lot of talent in India.

@KumarHemjeet

5 жыл бұрын

ohh..really ? Tell me any major invention done by indian . facebook - abroad ,google-abroad and amny more . We crave to study into MIT .. so why don't u just stfu !

It seems like Indian students are much more into theoritical education than the Mitians. Though we indians dont get practical education but the depth of questions we reach to is better than americans

@abadibi

6 жыл бұрын

you really didn't have to brag about that.

@sandraelsa671

6 жыл бұрын

Exactly you didnt have to do that

@angelmi1460

6 жыл бұрын

Well, it is not the only nation that does such "difficult" stuff😝

@Aer01614

6 жыл бұрын

That is a gross assertion that I’m confident you have no evidence for. Speaks volumes about your intellect and dare I say ego.

@lawliet2263

2 жыл бұрын

It seems to me that people from a third world country like iNdia shit on the streets

The good thing is Americans focus on learning and absorbing whereas we indians focus more in depth of the subject + cramming if we dont get it

Teaching is not good....