Question

The energy required to remove a body of mass $m$ from earth's surface is/are equal to:

• A. $\frac{-GMm}{R}$
• B. $mgR$
• C. $-mgR$
• D. none of these.

Answer 1

The correct option is B $mgR$

An object can be thrown up with a certain minimum initial velocity so that, the object goes beyond the earth's gravitational field and escape from earth, this velocity escape velocity of the earth.

potential energy at surface is $-\frac{GMm}{R}$, so kinetic energy that has to give to reach particle to infinite ( zero energy) is equal to potential energy.

$E=\frac{GMm}{R}=g.m.R$

so the best possible answer is option B.