Question

Give three examples when work done is zero.

Answer 1

Work done is zero when the displacement of the body is perpendicular to the force acting on it or when there is no displacement or when the net external force acting on the body is zero.

Mathematically expressed as:

$\mathit{W}\mathbf{=}\mathit{F}\mathit{s}\mathit{c}\mathit{o}\mathit{s}\mathit{\theta }$

Three examples are,

1. When we stand holding a bag in our hands and do not move it, as there is no displacement, thus the work done is zero.
2. If you push a wall and it doesn't move, work is not done as there is no displacement.
3. When we hold a bag on our head and walk horizontally such that the angle between the displacement and the gravitational force is ${90}^{\circ }$, thus, work done is zero.