Question

A person pushes a wall and believes that he is doing a work, while another person believes that this person did not work. Which belief is true?

Answer 1

In physics work is defined as force applied on an object times the displacement of the object, caused by the applied force. In the case of a person pushing the wall, the person applies a force on the wall but the wall undergoes no displacement. Hence the work done by the person is zero.

Another way to look at this situation is through work-energy theorem. This theorem tells us that work done on a system equals the change in kinetic energy of the system. As the wall does not move so the change in it's kinetic energy is zero. Hence the work done on the wall is zero.

So the other person is correct.