ICSE Class 10 Answered

The term  ' m g h ' is gravitational potential energy of mass m at a height h above earth surface or above some reference level.

Gravitational potential energy U(r) of a mass m is

where G is universal gravitational constant , M is mass of earth  and r is distance of mass m from center of earth.

Gravitational potential energy U(R) of a mass m on earth surface is

  ............................ (1)

Gravitational potential energy U(R+h) of a mass m at a height h above earth surface is

If we take earth's surface as reference , then potential energy of mass m at a height h above earth surface is

By neglecting (h/R)² and higher powers , we get

where  ( G M )/R² is acceleration due to gravity g on earth surface .

hence potential energy of mass m at a height h above earth surface = m g h .