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A body of mass 'm' kg starts falling fro...

A body of mass 'm' kg starts falling from a point 2R above the Earth's surface. What is its K.E. When it has fallen to a point 'R' above the Earth's surface.

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Potential energy ` U = (-GMm)/r = (GMm)/(R+h)`
`U_("intial") = -(GMm)/r and U_("final") = - (GMm)/(2R)`
Loss of P.E = gain in K.E = `(GMm)/(2R) - (GMm)/(3R) = (GMm)/(6R)`
` :. K.E = (GMm)/(6R)`
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