Work and Energy (question)

Question. What is the work done by force of gravity in he following cases ?
(a) Satellite moving around the earth in a circular orbit of radius 35000 Km
(b) A stone of mass 250 g is thrown up through a height of 2.5 m
Answer.
(a) Zero, as the displacement in one complete revolution is zero
(b) Given mass (m) = 250g = 0.25 Kg, height (h)=2.5m , g = 10 ms^2 , W = ?
Now , W=FS = mg×h = 0.25 × 10 × 2.5 = 6.25 J

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