Question

Has work been done in the following example?

An athlete running in a circular track at the same speed.

Answer 1

No (by the centripetal force).

In a circular path, the centripetal force acts towards the center of the track, while the athlete’s displacement at any instant is along the tangent (perpendicular to the force). Since the angle between the force and displacement is 90°, the work done by the centripetal force is zero (W = F . s . cos 90° = 0).