In one of the exercises to strengthen the wrist and fingers, a person squeezes and releases a soft rubber ball. Is the work done on the ball positive, negative or zero during compression? During expansion?
(i) During compression, the work done on the ball is positive as the direction of the force applied by the fingers is along the compression of the ball.
(ii) During expansion, the work done is negative as expansion takes place against the force applied by the fingers on the ball.