A body of mass m kg. starts falling from a

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A body of mass $m$ kg. starts falling from a point $2R$ above the Earth’s surface. Its kinetic energy when it has fallen to a point $‘R’$ above the Earth’s surface [$R-$Radius of Earth, $M-$Mass of Earth, $G-$Gravitational Constant]

A

$\frac{1}{2}\frac{{GMm}}{R}$

B

$\frac{1}{6}\frac{{GMm}}{R}$

C

$\frac{2}{3}\frac{{GMm}}{R}$

D

$\frac{1}{3}\frac{{GMm}}{R}$

A body of mass $m$ kg. starts falling from a point $2R$ above the Earth’s surface. Its kinetic energy when it has fallen to a point $‘R’$ above the Earth’s surface [$R-$Radius of Earth, $M-$Mass of Earth, $G-$Gravitational Constant]

Potential energy $U = \frac{{ - GMm}}{r} = - \frac{{GMm}}{{R + h}}$

${U_{initial}} = - \frac{{GMm}}{{3R}}$ and ${U_{final}} = - \frac{{ - GMm}}{{2R}}$

Loss in $PE$ = gain in $KE = \frac{{GMm}}{{2R}} - \frac{{GMm}}{{3R}} = \frac{{GMm}}{{6R}}$