5. A little boy tries to push a heavy cupboard. He uses a force of 400 N, but he is unable to move the heavy cupboard.
(a) How much work has he done?
(b) Explain your answer in (a).
(c) For work to be done, the following conditions must be satisfied:
(i) There must be a
acting on the object.
(ii) The object must
in the direction of the force.