Conservation of energy

The kinetic and potential energies are both different forms of the same basic quantity, i.e mechanical energy.
total mechanical energy of a body is the sum of the kinetic energy and potential energy.
in our previous discussion of a falling body, potential energy may change into kinetic energy and vice versa,
but the total energy remains constant.
Mathematically.
   total energy =P.E + K.E. =CONSTANT

                        

this is a special case of the law of conservation of energy which states that:
     Energy cannot be destroyed.it can be transformed from one kind into another,
     but the total amount of anergy remains constant.