Question

Write an expression for the potential energy of a body of mass m placed at a height h above the earth surface.State the assumptions made,if any.

Answer 1

We know that every object on the surface of the Earth is attracted by the Earth.So,if an object has a mass'm',it will experience a force that is called the weight of the object which acts vertically downwards.

To move this object upward from 'a' to'b' through a distance 'h', we must apply a force 'f' upward were F=Mg

W=Fh, but as F=Mg,

W=mgh -------(1)

This work done on the object which changes its position is called the Gravitational Potential Energy. Then:

Ep=w-------(2)

From (1) & (2), we get:

Ep=mgh