Question

A body of mass m is placed on the earth’s surface. It is taken from the earth’s surface to a height $h = 3 R$. The change in gravitational potential energy of the body is

• A. $\frac { 2 } { 3 } m g R$
• B. $\frac { 3 } { 4 } m g R$
• C. $\frac { m g R } { 2 }$
• D. $\frac { m g R } { 4 }$

Answer 1

Answer: (B)

$\frac { 3 } { 4 } m g R$

Answer 2

$\Delta U = \frac { m g h } { 1 + \frac { h } { R } } = \frac { m g \times 3 R } { 1 + \frac { 3 R } { R } } = \frac { 3 } { 4 } m g R$