Question

The Law of conservation of mechanical energy is valid only when…..

Answer 1

1. The law states that “in the absence of external and the non-conservative forces the total energy of the system, that is the sum of kinetic energy and the potential energy of the system is conserved”.
2. But this law is applied only when the work done by the external and non-conservative forces on the system is zero.

Thus, the conservation of mechanical energy is valid only when the external and non-conservative forces on the system are zero.