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A body at rest starts from a point at a ...

A body at rest starts from a point at a distance r (gtR) from the centre of the Earth. If M and R stand for the speed of the body when it reaches the Earth surface is

A

`sqrt((GM_e)/(R_e)`

B

`sqrt((3GM_e)/(2R_e))`

C

`sqrt((2GM_e)/(2R_e))`

D

zero

Text Solution

Verified by Experts

The correct Answer is:
B
Using energy conservation
`-(GM_e m)/(2R_e) + 1/2 m (sqrt((5 GM_e)/(2R_e)))^2 = 1/2 mv^2 `
`v = sqrt((3GM_3)/(2R_e))`.
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