The physics of skiing refers to the analysis of the forces acting on a person while skiing. The motion of a skier is determined by the physical principles of the conservation of energy and the frictional forces acting on the body. For example, in downhill skiing, as the skier is accelerated down the hill by the force of gravity, her gravitational potential energy is converted to kinetic energy, the energy of motion. In the ideal case, all of the potential energy would be converted into kinetic energy; in reality, some of the energy is lost to heat due to friction.