Assuming the radius of the earth as R, the change in gravitational

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Assuming the radius of the earth as R, the change in gravitational potential energy of a body of mass m, when it is taken from the earth's surface to a height 3R above its surface, is

Gravitational potential energy (GPE) on the surface of earth,

E₁ = -	G M m
	R

GPE at 3R, E₂ = -	G M m	= -	G M m
	(R + 3R)		4R

∴ Change in GPE = E₂ - E₁ = -	GMm	+	GMm	=	3GMm
	4R		R		4R

=	3g R²m		∵ g =	GM
	4R			R²

=	3	mg R
	4

	3	mgR
	4

	3	mgR
	2