gravpe

# gravpe - Gravitational Potential Energy THEORY Recall the...

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Gravitational Potential Energy THEORY Recall the change in potential energy of a system, V, is related to the work, W, by the force one part of the system exerts on the other, U - W = W ext where W ext is the work by an external force against the gravity force. We can think of this external work as the energy needed to stretch the gravitational bond between two masses. Given two point masses, M and m, initially separated by a distance r i then M attracts m with a force of magnitude, F = GMm/r 2 . If an external force is applied with the above magnitude it can move m from r i to a distance r f > r i . Then the external force does positive work on m given by, r f W ext = GMm dr/r 2 = - GMm ( 1/r f - 1/r i ) > 0. r i Therefore, the change in gravitational potential energy of this two-particle system equals W ext this result, U = U(r r ) – U(r i ) W ext = - GMm ( 1/r f - 1/r i ). Setting r

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gravpe - Gravitational Potential Energy THEORY Recall the...

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