Discuss the possibilities of work done to be zero.

Explanation

(i)When the force is zero (F=0). For example , body moving on a horizontal smooth frictionless sueface will continue to do so as no force (not even friction) is acting along the plane .
(ii)When the displacment is zero (dr=0). For example when force is applied on a rigid wall it does not produce any displacement . Hence, the work is zero as shown in figure.
(iii) when the force and displacement are perpendiculer `(theta=90^(@))` to each other, When a body move on horizontal direction the gravitational force (mg) does not work on the body, since it acts at right angle to the displacment as shown in figure (b) . In circuler as it is motion the centripetal force does not do work on the object moving on a circle as it is always perpendiculer to the displacement as shown in figure (c).