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Question
A satellite revolves around the earth in a circular orbit. What is the work done by the force of gravity? Give reason.
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Solution
The centripetal force, which generates the force of gravity, does no work. The satellites have accomplished nothing at all. This is due to the fact that the Earth is the satellite's centre of mass and that the displacement is always along the tangent to the circular route, or normal to the direction of force on the satellite. (θ = 90°)
Displacement of satellite is normal to the direction of force
where, O - Earth, S - Displacement, F - Force of gravity
W = F × S cos 90°
W = F × S × 0 = 0
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