When the roller coaster moves downwards, kinetic energy is generated. The maximum kinetic energy generated is when the roller coaster is at the bottom of the track. When it begins to go up, the kinetic energy converts to potential energy.

In a roller coaster, kinetic energy is the energy of motion that actually moves the train along the track. The process begins with potential energy, which is built up as the coaster is pulled to the top of the first large hill (the lift hill). Once the train crosses the peak and begins its descent, gravity takes over and converts that stored potential energy into kinetic energy. The faster the coaster travels, the more kinetic energy it possesses, according to the formula KE=21​mv2. Throughout the ride, there is a constant exchange: as the coaster climbs another hill, it slows down because kinetic energy is being converted back into potential energy. When it drops again, the potential energy turns back into kinetic. This "energy loop" continues until the end of the ride. However, not all energy is perfectly recycled; some kinetic energy is always lost to thermal energy due to friction between the wheels and the track and air resistance. Engineers must carefully calculate these losses to ensure the coaster has enough kinetic energy to clear every loop and return safely to the station without stalling on a hill.