Since roller coasters don't have engines, they must be pulled by a motorized chain to the top of the first big hill. As the roller coaster rises higher and higher into the air, its potential energy keeps growing until it reaches its maximum potential energy at the crest of the hill.

Roller coasters are primarily powered by the conversion of potential energy into kinetic energy, though the initial "boost" comes from several mechanical sources. Most traditional coasters use a motorized chain lift to pull the train to the top of the first hill, where gravity then takes over for the remainder of the ride. Modern "launched" coasters, however, use more advanced technology to achieve high speeds instantly without a lift hill. These systems include Linear Induction Motors (LIM) or Linear Synchronous Motors (LSM), which use powerful electromagnets to propel the train forward. Other methods include hydraulic launches, which use pressurized fluid and a winch system, and pneumatic launches, which utilize compressed air. In some older or specialized designs, flywheels, friction wheels, or even weighted catapults have been used to provide the initial force. Regardless of the launch method, the coaster's ability to complete its circuit relies on minimizing friction and managing energy as it moves through various inversions and turns.