In most circumstances, the normal force acting on an object and the force of static friction do no work on the object. However, the reason that the work is zero is different for the two cases. In each case, explain why the work done by the force is zero.

Normal force acts perpendicular to displacement hence angle between force and displacement is 90 degree.

work done = Fd cos θ

θ = 90

work done = 0

In case of static friction, there is no displacement.

work done = force x displacement

= force x 0

= 0

work done therefore will be zero.