In an amusement park the most thrilling rides let the rider experience the largest fictitious forces. Fictitious forces are experienced in accelerating reference frames. The seat or cart in which the rider is sitting is accelerating, because it is speeding up, slowing down, or turning rapidly. A ride that is just moving you along with constant velocity will probably not excite you. You might as well be in your car on the freeway with the cruise control engaged.
Roller coasters offer thrilling rides.
The cart descends on a track down a very steep slope. Assume the top of the hill is 50m above the ground. The gravitational potential energy of a object on top of the hill is Mgh. Neglecting friction, this potential energy has been converted into kinetic energy when the object reaches the bottom of the hill. The forces on the object as it descends are the force of gravity and the support from the track.