Question

Why is work done by a coolie shifting load on his head on a railway platform zero?

Answer 1

Definition of work done

1. Work is said to be done when a body moves through a certain distance under the effect of a force applied to it.
2. It is given as, $W=FS\cos \theta$, where, $F$ is force, $S$ is displacement and $\theta$ is the angle between the direction of force and direction of displacement.

The reason for work done by coolie is zero is:

1. When the coolie carries a load on his head, the force of gravity acts on him.
2. Therefore, the direction of force is vertical while the direction of displacement is horizontal.
3. Hence, the angle between the direction of force and direction of displacement is ${90}^{\circ }$
4. So, work done $\left(W\right)$ by coolie will be zero.

$$\begin{gathered} W=FS\cos \theta \\ W=FS\cos 90° \\ W=FS\times 0 \\ W=0 \end{gathered}$$

Therefore, the work done by a coolie shifting load on his head on a railway platform is zero because the direction of force is perpendicular to the direction of displacement.