Question

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

Answer 1

Acceleration due to gravity on earth's surface$=g=\frac{GM}{R^2}$.

Gain in potential energy=$\frac{GMm}{R}-\frac{GMm}{2R}=\frac{GMm}{2R}=\frac{1}{2}mgR$