How does a roller coaster continue to move through the twists and turns of a track if it only uses an engine at the very beginning?

A roller coaster relies on gravitational potential energy to continue moving through its twists and turns after the initial push from the engine. When the coaster is lifted to the highest point, it stores energy, which converts to kinetic energy as it descends. As it navigates the track, the momentum gained from the initial height keeps it moving, while the design of the track helps maintain speed through curves and loops. Friction and air resistance slow it down, but the coaster's initial elevation ensures it can complete the ride.