A block sits on a slight incline, held at rest by the frictional force between the block and the incline. Which of the following statements is true?
A) The frictional force performs no work, since there is no motion of the block.
B) The work by the frictional force is equal to the gravitational potential energy of the block.
C) The work done by the frictional force is negative, since the force of friction opposes the direction that the block is being tugged by gravity.
D) The work done by gravity is entirely converted into heat because of the friction present.
E) None of these is true.

Question

Quizplus · Accepted Answer

The frictional force indeed performs no work on the block because there is no displacement. Work is defined as the force applied over a distance, and since the block does not move, the distance is zero, making the work done by friction zero as well.

A Block Sits on a Slight Incline, Held at Rest