Consider the three situations given below:
(1) A boy pushes his bicycle forward along a straight road.
(2) A girl presses hard against a wall, but the wall does not move.
(3) A student gently lowers a heavy bucket to the ground using a rope.
a. (a) For each situation, state whether the work done by the applied force is positive, negative or zero. Give one reason for each answer.
b. (b) Among the three situations, identify the one in which the applied force removes energy from the object. Explain your choice briefly.