Answer:
When
an object is raised through a certain height above the ground, its energy increases.
This is because the work is done on it, against gravity. The energy present in
such an object is called gravitational potential energy. Thus, the gravitational
potential energy of an object at a point above the ground is denned as the work
done in raising it from the ground to that point against gravity. Consider a
body of mass m lying at point P
on the Earth's surface, where its potential
energy is taken as zero.
As weight, mg acts vertically downwards, so to lift the
body to another position Q at a height h.
we have to apply a minimum force which is equal to mg in
the upward direction.
Thus, work is done on the body against the force of
gravity.
We know that,
Work done, W = Fs ...(i)
As F = mg and s = h
Putting these values in equation (i), we get
W = mg X h = mgh
This work done on the body is equal to the gain in energy
of the body. This is the potential energy of the body.
Potential energy P.E. = mgh
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