1.

A body of mass m is raised through a distance equal to the radius of the earth from earth's surface. The change in P.E. will be:

Answer»

mgR
2 mgR
3 mgR
`(1)/(2)` mgR.

Solution :`U_(1)=(-GMM)/(R ), U_(2)=(-GMm)/(R +R)`
`DeltaU=U_(2)-U_(1)=(GMm)/(R )[-(1)/(2)+1]=(GMm)/(2R)=(gR^(2)m)/(2R)`
`=(1)/(2)mgR`.
Thus CORRECT choiceis (a).


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