Roller coasters are fascinating machines that primarily use the physics of gravity and inertia to move around the track without an internal engine. The journey typically begins with a lift hill (using a chain or cable) or a hydraulic/magnetic launch that provides the train with a massive amount of Potential Energy. Once the train reaches the highest point and begins its descent, this potential energy is converted into Kinetic Energy (energy of motion). In 2026, modern steel coasters use tubular tracks and polyurethane wheels to minimize friction, allowing the train to maintain enough momentum to clear loops, hills, and corkscrews. For safety, coasters use a "three-wheel" system: running wheels on top, side-friction wheels on the sides, and "up-stop" wheels underneath to lock the train to the track even when inverted. This high-value engineering ensures that gravity provides the thrills while the track and wheel design provide the absolute safety and control required for high-speed maneuvers.