In each of the following a force F is acting on an object of mass m.

The direction of displacement is form west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.

Explanation

(a) In the first case [Figure (i)],the direction of force F and the direction of displacement are at right angles to each other. So, the work done in the first case is zero.
(b) In the second case [Figure (ii)], the displacement is in the direction of force F, so the work done is positive.
(c) In the third case [Figure (iii)], the force F acts in a direction opposite to the direction of displacement, so the work done is negative.