Explain the law of conservation of energy .

Explanation

The total mechanical energy of the system is conserved if the forces doing work on it are conservative . If some of the force involved are non-conservative, part of the mechanical energy may get transformed into other forms such as heat, light and sound. However, the total energy of an isolated system does net change, as long as one accounts for all forms of energy . Energy may be transformed from one form to another but the total energy of an isolated system remains constant. Energy can neither be created, nor destroyed
Since the universe as a whole may be viewed as an isolated system, the total energy of the universe is constant. If one part of the universe looses energy , another part must gain an equal amount of energy