WAEC Physics 2018 Paper

Concept:Centripetal force is perpendicular to the motion of the body, so no work is done on it.Explanation:Work done by a force is given by $W = Fd\cos\theta$, where $\theta$ is the angle between the force and the displacement.In a uniform circular motion, the centripetal force always points toward the center of the circle.The body's instantaneous displacement is always along the tangent to the circle, which is perpendicular to the radius.Thus, $\theta = 90^\circ$, and $\cos 90^\circ = 0$.Therefore, $W = Fd \times 0 = 0$.The centripetal force only changes the direction of the body, not its speed, so no energy is transferred to it.Answer:The work done by the centripetal force on the body is zero, so the correct option is B.