Question

A satellite revolves around a planet in a circular orbit. What is the work done by the satellite at any instant? Give a reason.​

Answer 1

When the satellite revolves around the earth then centripetal force acts towards the centre that is towards the earth and the displacement is tangential as shown in the figure.

So, the angle between $F$ and $S$ is ${90}^{\circ }.$

Therefore, the work done = $F\times S\cos \theta$

$⟹$ $F\times S\cos {90}^{\circ }$

$⟹$ zero ($\because \cos {90}^{\circ }=0$)

So, the work done by the satellite on earth at any instant is zero.