Question

Work done is said to be zero if the applied force is _____ to the direction of displacement.

Answer 1

Work Done:

1. Work done (W) is the dot product of force (f) and displacement (d).
2. The expression is with angle $\theta$ between force and displacement vector,
   $$\begin{gathered} W=F.d \\ W=Fd\cos \theta \end{gathered}$$
3. The work done is zero only when $\theta ={90}^o$ that is applied force is perpendicular to displacement vector.

Hence, Work done is said to be zero if the applied force is perpendicular to the direction of displacement.