Kinetic energy needed to project a body of mass m from earth's surface (radius R ) to infinity i

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7.Gravitation

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The kinetic energy needed to project a body of mass $m$ from the earth's surface (radius $R$) to infinity is

A

$\frac{{mgR}}{2}$

B

$2mgR$

C

$mgR$

D

$\frac{{mgR}}{4}$

Solution

$-\frac{\mathrm{GM}_{\mathrm{E}} \mathrm{m}}{\mathrm{R}}+\mathrm{K} \cdot \mathrm{E} \cdot=0+0$

$\mathrm{K.E}=\frac{\mathrm{GM}_{\mathrm{E}} \mathrm{m}}{\mathrm{R}}=\frac{\mathrm{GMe}}{\mathrm{R}^{2}} \cdot \mathrm{mR}=\mathrm{mgR}$

Standard 11

Physics

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