question_answer

A body of mass m is placed on earth's surface. It is then taken from earth's surface to a height \[h=3R,\] then the change in gravitational potential energy is:               [AIPMT 2002]

A) \[\frac{mgh}{R}\]

B) \[\frac{2}{3}\,mgR\]

C) \[\frac{3}{4}mgR\]

D) \[\frac{mgR}{2}\]

Correct Answer: C

Solution :

Key Idea: The gravitational potential energy of mass m in the gravitational field of mass M at distance r from it is .

From key idea, potential energy

At earth's surface,

Now, if a body is taken to height  then the potential energy is given by

Thus, change in gravitational potential energy,