When riding a roller coaster, gravity is one of the main forces. When the cart on the roller coaster travels to the top of the hill, it’s the acceleration due to gravity that brings it back to the start. When the cart gets to all the way up to the top of the hill, gravity ends up pulling it down. The cart starts at a slow pace but gets faster as it approaches the bottom. As it begins to climb to the next hill, the speed slows down. This is because the acceleration due to gravity is 9.81 m/s^2. As the roller coaster cart begins its fall from the lift, its velocity increases which causes the cart to gain kinetic energy. So therefore the faster the cart moves, the more kinetic energy it gains.