Question

A body of mass m is placed on earth surface which is taken from earth surface to a height of h = 3R then change in gravitational potential energy is :

• A. $\frac{mgR}{4}$
• B. $\frac{2}{3}mgR$
• C. $\frac{3}{4}mgR$
• D. $\frac{mgR}{2}$

Answer 1

Answer: (C)

$\frac{3}{4}mgR$

Answer 2

The correct option is (C) : $\frac{3}{4}mgR$

Change in G.P.E. = final energy – initial energy
= $-\frac{GMm}{4R}+\frac{GMm}{R}$ = $\frac{GMm}{R}[\frac{1}{\frac{1}{4}}]$
$\frac{3}{4}\frac{GMm}{R}=\frac{3}{4}\frac{GM}{R^2}mR=\frac{3}{4}gmR$