Question

examples of when work done is zero

Answer 1

when displacement and force are at 90deg, when displacement is zero, when force is zero, net force is zero, when rate of change of displacement is zero, when velocity of the body accelerated is constant with time,....and many more cases work done is zero.

Answer 2

Work is said to be done only when the force applied on a body makes a body move (i.e. there is displacement of the body). It is the product of the force and displacement of the point of application of the force in the direction of force.

Work done is said to be zero when a force acts on a body but the body doesnot move i.e., displacement is zero.

Example...
1)Pushing a wall

2)A coolie does no work while standing with a heavy load on his head ( although he feels tired)

3) A small boy pushing a heavy stone