Question

Under what category can the frictional force acting on a spinning coin be classified as? Is it kinetic or rolling?

Answer 1

I think its rolling friction

Answer 2

can you please explain how.

Answer 3

There are 3 types of friction, reacting to 3 types of relative motion of body wrt its base.

- kinetic fr. (represented by a force) if slipping occurs
- rolling fr. (repr. by a torque) if rolling occurs (angular velocity parallel to tangent plane between body and base)
- pivoting fr. (repr. by a torque) if swivelling/spinning occurs (angular velocity normal to tangent plane between body and base)

Answer 4

Of course, you can have any combination of kinetic/rolling/pivoting friction for a complex motion.

Answer 5

So which combination do you think would exist in this case?

Answer 6

pivoting and rolling?

Answer 7

Is it an open question or do must you give a specific answer?

I would say pure pivoting in an ideal case; but in the real world, rather rolling (on one of the two edges) + pivoting. Some non-working static friction should also be there.

Answer 8

Okay. I get it now. thanks.