Question

Rolling motion:
when an object rolls without slipping and moves with a constant angular velocity, why is friction 0?

Answer 1

i understand that there will be no kinetic friction due to 0 relative velocity but what about static friction?

Answer 2

If the angular velocity is constant , what is alpha?

Answer 3

Hint: Draw a FBD of the wheel and apply the sum of the external torques = I* alpha.
From this, you can solve for the magnitude of the force of friction.

Answer 4

Well, in your question you mentioned it's rolling with CONSTANT angular acceleration, therefore cannot the friction be dismissed? Also, static friction works when an object has to overcome a certain amount of friction to begin moving. This object is already moving at a constant acceleration so \(f_s\) is also dismissed.

That's my take on it, not quite sure if it's 100% correct.

Answer 5

true that the net torque is 0 and so friction must be 0

Answer 6

then how would there be no sliding. Like, what is it that keeps the object in contact with the ground without sliding?

Answer 7

You really need to draw out a Free Body Diagram.

Answer 8

Did you draw the FBD? If so, the answer is right there

Answer 9

sure. it makes sense mathematically

Answer 10

its just that im confused. but anyway, im going to close this question. Thanks for all the help

Answer 11

Label them.

Answer 12

whats that? how'll that roll?

Answer 13

BTW, @Jhannybean the question says constant angular velocity not constant angular acceleraion.

Answer 14

i have another question. so, ill close this one

Answer 15

...:) Typo!