At the highest point on the roller coaster (assuming it has no velocity), the object has a maximum quantity of gravitational potential energy and no kinetic energy. As the object begins moving down to the bottom, its gravitational potential energy begins to decrease and the kinetic energy begins to increase.

A roller coaster ride is a constant cycle of energy transformation governed by the Law of Conservation of Energy. It begins with Gravitational Potential Energy (GPE), which is stored as the train is pulled to the top of the first lift hill (GPE=mgh). As the train crests the hill and drops, this stored GPE is converted into Kinetic Energy (KE), the energy of motion (KE=21​mv2). At the bottom of a drop, KE is at its maximum and GPE is at its minimum. As the train ascends the next hill, the process reverses: KE is converted back into GPE. However, the system is not 100% efficient; some energy is always "lost" as thermal energy (heat) and sound due to friction between the wheels and the track. This is why the first hill must always be the tallest; the train simply wouldn't have enough total mechanical energy to reach the top of a taller subsequent hill. Engineers in 2026 use complex simulations to ensure that the initial "energy budget" is sufficient to complete the entire circuit.