question_answer 52)

                  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 force of friction between the block and incline? Is there then a dissipation of energy?                

Answer:

                  When cart moves forward with constant speed, block resting on the incline tends to move backward due to inertia of rest. To keep the block at rest, work is done by the force of friction. Since, there is no relative motion between the block and incline, so there is no dissipation of energy.