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Question
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
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Solution
When a satellite orbits the earth, its displacement over a short period of time is along the tangent to the satellite's circular route. The gravitational force (F) exerted on the satellite due to the earth is along the radius depicted in the picture.
Because a tangent is always perpendicular to the radius, both displacement and force are perpendicular. The satellite experiences no displacement in the direction of the force, i.e., s = 0. As a result, the force of gravity on the satellite produces no work since W = F × s = 0.
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