Q:

Friction & relative motion

If there are two bodies that have zero relative velocity, does that mean friction will not exist between them, since friction opposes relative motion. In the figure below i have two wheels A&B, with A rotating in clockwise sense and B in anti-clockwise sense. Suppose they are in contact at point p, then since linear velocity is tangent to the circle and in the direction of motion, therefore linear velocity at p will be in downwards direction for both A and B. Now, if the magnitude of their linear velocity is also same, then relative velocity of A with respect to B, will be zero at p. Will that mean  frictional force on A(because of B) be zero at p?

A:

If the two surfaces are moving with the same velocity it means there will be no kinetic friction.  There may well be a force of static friction acting between the wheels.

