The first law of thermodynamics, which is a fundamental law of physics, requires the transformation of kinetic energy, potential energy and heat energy when a deputy sheriff rides a horse while directing traffic. The precise transformations depend on the activities of the horse and the sheriff.
According to the Encyclopedia Britannica, the first law of thermodynamics embodies the principle that energy can neither be created nor destroyed. It can only be transformed from one form to another. When the deputy sheriff and the horse stand perfectly still, heat energy is being converted to kinetic energy as their hearts beat, blood flows, and they breathe and blink. When the officer raises a hand to halt traffic, the kinetic energy of the motion is transformed to the potential energy of a raised hand. When the horse moves from one location to another, kinetic energy is transformed to heat energy as the horse's muscles contract and relax.