What is the significance of the law of conservation of energy in science and technology?

The law of conservation and transformation of energy provides a scientific basis for various calculations in all areas of science and technology. For example, in mechanics, knowing the internal energy of a stationary body, we can find what maximum kinetic energy it can acquire (projectile), knowing the potential energy of fuel combustion, we can predict which fuel is better (engine). As a result of the discovery of the law of conservation of energy, for example, it was proved that it is impossible to create a perpetual motion machine of the first (when it works, energy is released) and the second kind (works forever, from one “push”). Knowing the energy balance of a system, scientists and engineers can predict how much of the energy can be converted into “useful” work.