A ball is being twirled in a circle at the end of a string.?

Question

The string provides the centripetal force needed to keep the ball moving in the circle at a constant speed. Does the force exerted by the string on the ball do work on the ball in this situation? Explain.

Answer 1

No. Work is the scalar product of force and distance, which considers only the component of the force that is in the same dimension as the distance. In your example, the force is perpendicular to the distance, so no work can be done.

Another way to look at it: Work = change in kinetic energy. But if the ball is moving at constant speed, the kinetic energy isn't changing - therefore no work is being done.