The roller coaster uses many types of forces but the one you feel often is gravity. The reason you feel gravity on a roller coaster is because of acceleration or the change of speed. There are only two forces gravity and acceleration are caused by gravitational attraction. Gravitational attraction is when a particle attracts every other particle that is proportional of mass and the distance between them. When acceleration and gravity apply the same force they cancel each other out making you feel weightless. But when they are in the same direction you feel heavy. Also that the roller coaster pushes your body in different directions. Also the train when it's slowing down or changing direction it is accelerating.
