What is the work done by the force of gravity on a satellite moving round the Earth ? Justify your answer.

Explanation

When a satellite moves around the Earth, its displacement in a short interval is along the tangent to the circular path of the satellite. The gravitational force (F) acting on the stellite due to the Earth is along the radius as shown in fig.

Since a tangent is always perpendicular to the radius, the displacement and the force are perpendicular to each other. There is no displacement of the satellite in the direction of the force, i.e., s= 0. Thus, work done by the force of gravity on the satellite is zero as W = F xx s= 0.