Question

Is it possible that a force acts on a body, and still work done is zero ? Support your answer by two examples.

Answer 1

1. No work is done, when a force acts at right angles to the direction of displacement.
2. It is because in such a situation displacement in the direction of force is zero.
3. $Workdone\left(W\right)=Force\left(F\right)\times displacement\left(s\right)\cos \left(\theta \right)$
4. $W=F\times s\cos \left(\theta \right)$
5. $W=F\times s\cos \left({90}^0\right)$
6. $\therefore W=0[\cos \left({90}^0\right)=0]$

Examples:-

1. A person carrying a suitcase vertically in his hand walks in a horizontal direction, no work is done, because the angle between the direction of force applied by hand and the direction of displacement is ${90}^0$.
2. Earth revolving around the sun, is not doing any work.