1.

The minimum speed with which a body must be thrown to reach a height of (R )/(4) above the surface of earth is :

Answer»

`sqrt(g (R )/(2))`
`sqrt(GR)`
`sqrt((2)/(5)gR)`
`sqrt(g(R )/(5))`.

Solution :Here `(1)/(2)MV^(2)=U_(2)-U_(1)=(-GMm)/((5)/(4)R)-((-GMm)/(R ))`
`rArr v=sqrt((2GM)/(5R))=sqrt((2)/(5R)*gR^(2)) = sqrt((2)/(5)gR)`
Thus CORRECT choice is (C ).


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