Question

A body of mass m kg starts falling from a point at height 2r

Answer 1

then catch it.................

Answer 2

Question:

A body of mass m kg starts falling from a point at height 2r above the earth's surface?

Answer :

A body of mass m kg starts falling from a point 2R above the earth’s surface. Its K.E. when it has fallen to a point ‘R’ above the Earth’s surface = ………..J [R – Radius of Earth, M-mass of Earth G-Gravitational constant]

PE = U = [(– GMm) / r] = [(– GMm) / (R + h)]

initially h = 2R, hence U1 = [(– GMm) / (R + 2r)]

= [(– GMm) / (3R)] then h = R, hence

U2 = [(– GMm) / (R + R)] = [(– GMm) / (2R)] loss in,

PE = U2 – U1(considering magnitude) =

[(GMm) / (2R)] + [(GMm) / (3R)] = [(GMm) / (6R)]

=> (1/6)[(GMm) / R]

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