Suppose we put a ball at rest on a rug and then start pulling the rug out from under the ball in a certain direction. The ball rolls without slipping on the rug as the rug moves under it. The friction force that the contact interaction between the rug and ball exerts on the ball does

Question

Quizplus · Accepted Answer

The friction force between the rug and the ball acts in the direction of the rug's movement, which is the same direction the ball moves. Since the force and the ball's displacement are in the same direction, the work done by friction on the ball is positive.

Suppose We Put a Ball at Rest on a Rug