Q. How much energy will be necessary for making a body of 500 kg escape from the earth [ g = 9.8 $ms^{- 2},$ radius of earth = $6.4 \times 10^{6}$m]
A) About $9.8 \times 10^{6}$J
B) About 6.4$\times 10^{8}$J
C) About 3$.1 \times 10^{10}$J
D) About $27.4 \times 10^{12}$J
Explanation
(c) Potential energy of a body at the surface of the earth
$PE = - \frac{GMm}{R} = - \frac{9R^{2}M}{R} = - mgR$
$= 500 \times 9.8 \times 6.4 \times 10^{6}$
$= - 3.6 \times 10^{10}J$
So, if we give this amount of energy in the form of kinetic energy then body escape from the earth
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.