Explanation

The law of conservation of energy is based on the principle of Bernoulli's theorem.

Bernoulli's theorem states that in a steady flow of an incompressible, frictionless fluid, the total mechanical energy (sum of potential energy, kinetic energy, and pressure energy) per unit mass of the fluid remains constant along a streamline.

This means that the total energy of the fluid is conserved as long as no external forces are acting on it, such as friction or heat transfer.