Q.22 A rough inclined plane is placed on a cart moving with a constant velocity u on horizontal ground. A block of mass M rests on the incline. Is any work done by a force of friction between the block and incline? Is there then a dissipation of energy?

Hint: Work done depends on the displacement of the point of application of force.
Step 1: Interpret the work done by frictional force.
Consider the adjacent diagram. As the M is at rest

Hence, f = frictional force = Mg sin θ

The force of friction acting between the block and incline opposes the tendency of sliding of the block. Since the block is not in motion, therefore, no work is done by the force of friction,

Hence, no dissipation of energy takes place.