Q.

Energy required to place a body of mass m from an orbit of radius 2R to 3R is (Given that M = mass of earth, R = Radius of Earth)

1 GMm3R  
2 GMm12R  
3 GMm18R  
4 GMm6R  

Ans.

(2)

ΔE=TE(3R)-TE(2R)

ΔE=-GMm6R+GMm4R=GMmR[14-16]

ΔE=GMmR[6-424]=GMm12R