Gravitation: Gravitational PE — Two Masses MCQ

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Gravitational PE — Two MassesHardQuestion 30750

Question

Two masses M and m (initially separated by ∞) are brought to separation r. Work done by gravity is:

GMm/r

PE at ∞ = 0. PE at r = −GMm/r. Work done by gravity = ΔPE (lost) = 0 − (−GMm/r) = GMm/r (positive — gravity does positive work as masses approach).