Can Friction Be Zero for a Rolling Sphere on a Surface?

[a.ratnaparkhi]

Homework Statement

A spherical body is rolling on a rough surface.
then "the frictional force may or may not be zero"
Is this statement is correct or not?
we discussed about this in classroom.
Some were saying it must not be zero and others were saying it may be zero.
Which is correct?

 

[Doc Al]

Homework Statement

A spherical body is rolling on a rough surface.
then "the frictional force may or may not be zero"
Is this statement is correct or not?

How can it not be, since it covers all bases.

we discussed about this in classroom.
Some were saying it must not be zero and others were saying it may be zero.
Which is correct?

Depends. Is it rolling without slipping? Is the surface horizontal?

 

[ashishsinghal]

How can it not be, since it covers all bases.

What do you mean by this line. I did not get you.

 

[ashishsinghal]

A spherical body is rolling on a rough surface.
then "the frictional force may or may not be zero"

Is any net external force or net torque (without considering friction) acting on the body?
If not then no friction force is acting. this is because:
Since it is purely rolling the point of contact has zero velocity with respect to the surface and also there is no acceleration of any form which has to be canceled by friction.

when there is any net force or torque friction tries to oppose it eg sphere rolling down an incline. but here there is no such problem

 

[gomunkul51]

define a "rough surface" and it's interaction with the rolling body.

 

[ashishsinghal]

here rolling and rough surface imply that pure rolling is taking place (without slipping) and the surface is capable of providing friction. Suppose this question is asked to you in an exam would ask such a question.

 

[a.ratnaparkhi]

Yes the surface is horizontal.Now, my opinion is if the surface suddenly becomes smooth then this body will start slipping i.e pure translational motion will start.
So, Without friction, it will not roll.
am I correct?

 

[Doc Al]

Now, my opinion is if the surface suddenly becomes smooth then this body will start slipping i.e pure translational motion will start.
So, Without friction, it will not roll.
am I correct?

If it's already rolling, what will change that if there's no friction?