Question

If g is the acceleration due to gravity on the earth’s surface, the gain in the potential energy of an abject of mass m raised from the surface of earth to a height equal to the radius of the earth R, is

• A. $\frac { 1 } { 2 } m g R$
• B. $2 m g R$
• C. $m g R$
• D. $\frac { 1 } { 4 } m g R$

Answer 1

Answer: (A)

$\frac { 1 } { 2 } m g R$

Answer 2

Work done = gain in potential energy $= \frac { m g h } { 1 + h / R }$

$= \frac { m g R } { 1 + R / R } = \frac { 1 } { 2 } m g R$ [As h = R (given)]