Q.

A body of mass m is taken from the surface of earth to a height equal to twice the radius of earth (Re). The increase in potential energy will be ______.            [2026]

(g is acceleration due to gravity at the surface of earth)

1 12mgRe  
2 34mgRe  
3 14mgRe  
4 23mgRe  

Ans.

(4)

U1=-GMmRe

U2=-GMmRe+2Re=-GMm3Re

ΔU=U2-U1=-GMm3Re+GMmRe

ΔU=23GMmRe=23[GMRe2](mRe)

⇒ΔU=23mgRe