Question

The moon revolves around the earth because the earth exerts a radial force on the moon. Does the earth perform work on the moon ?

• A. No
• B. Yes, sometimes
• C. Yes, always
• D. Cannot be decided

Answer 1

The correct option is A No

The work done is zero.

Work done is defined as the scalar product of force and displacement i.e W = F.s Cos$\theta$ where $\theta$ is the angle between force and displacement vector

The radial force exerted on the moon by the earth is perpendicular in direction i.e $\theta$ is at 90 degree

W = F.s Cos 90 = 0 (since Cos 90 = 0)

Thus work done is zero