Q. If mass of earth is $M$, radius is $R$ and gravitational constant is $G$, then work done to take $1\ kg$ mass from earth surface to infinity will be
A) $\sqrt{\frac{GM}{2R}}$
B) $\frac{GM}{R}$
C) $\sqrt{\frac{2GM}{R}}$
D) $\frac{GM}{2R}$
Explanation
(b) Potential energy of the $1\ kg$ mass which is placed at the earth surface $= - \frac{GM}{R}$
Its potential energy at infinite = 0
$\therefore$ Work done = change in potential energy $= \frac{GM}{R}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.