Question

We know that there is a relationship between work and mechanical energy change. Whenever work is done upon an object by an external force (or non-conservative force), there will be a change in the total mechanical energy of the object. If only internal forces are doing work then there is no change in the total amount of mechanical energy. The total mechanical energy is said to be conserved. Think of a real-life situation where we make use of this conservation of mechanical energy (where we can neglect external forces for the most part).

Describe your example and speak to both the kinetic and potential energy of the motion.

Answer 1

We can think of a bomb initially moving in the air horizontally. Here we ignore the gravity so we can ignore external gravitational force acting on it. It's having a kinetic energy, but zero potential energy as we are considering the line of motion of bomb as reference line. Now due to some chemical changes, it explodes into few parts. Direction and speed of each part will be such that the final momentum remain equal to initial momentumof the bomb. Any decrease in total kinetic energy of the fragments is equal to increase in potential energy.