Question

how can you justify that simple pendulum/loaded spring follows law of conversation of energy??​

Answer 1

Ignoring friction and other non-conservative forces, we find that in a simple pendulum, mechanical energy is conserved. All of the energy in the pendulum is kinetic energy and there is no gravitational potential energy. However, the total energy is constant as a function of time.

Answer 2

Justify the law of conservation of energy from the vibrations of a simple pendulum. At point 'A' velocity of the bob of simple pendulum is zero. Therefore, K.E. at point 'A' = 0. Since the bob is at a height (h), Therefore, P.E. of the bob will be maximum.