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Potential Energy

o Potential energy is the energy stored in the body or a system by virtue
of its position in field of force or by its configuration.
o Force acting on a body or system can change its Potential Energy.
o Few examples of bodies possessing PE are given below
i) Stretched or compressed coiled spring
ii) Water stored up at a height in the Dam possess PE
iii) Any object placed above the height H from the surface of the earth
possess PE
o Potential energy is denoted by letter U.
o All bodies fall towards the earth with a constant acceleration known as
acceleration due to gravity.
o Consider a body of mass m placed at height h above the surface of the
earth as shown below in the figure.

o The force acting on this body is the gravitational pull of the earth m×g
which acts in the downwards direction.
o To lift the body above the surface of the earth, we have to do work
against the force of gravity. Now, Work Done= Force × distance =
m×g×h
Where,
m= mass of the body;
g= acceleration due to gravity;
h= height of the body above the reference point, say the surface of
earth.
o Since work done on the object is equal to mgh, an energy equal
to mgh is gained by the object. Ep=mgh
Here from the above equation we see that potential energy of any
object at a height depends on the ground level or the zero level you
choose.
o One important point to note hare is that work done by gravity depends
on the difference in vertical heights of the initial and final positions of
the object and not on the path along which the object is moved.