What is zero work and can you give some examples?

Question

Note: Answer this question seriously.

Answer 1

when the force acts opp. to the direction then the work done is negative and vice versa. for eg. when we lift a book from the table work done by us is + BUT THE WORK DONE BY GRAVITY IS - SINCE ITS ACTING DOWNWARDS.  when the force ie perpendicular to the displacement then the work done is zero.eg wok done by gravity on moving bus