Question

The kinetic energy needed to project a body of mass $m$ from the earth's surface (radius $R$ ) to infinity is :

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

Answer 1

Answer: (C)

The minimum kinetic energy required to project a body of mass $m$ from earth's surface to infinity is known as escape energy. Therefore,
$KE =\frac{G M_{e} m}{R}=m g R$
$\left(\because g R=\frac{G M_{e}}{R}\right)$