Roller coasters

    
(a) The first tower                                                            (b) Twists and turns
Fig. 13-5: Roller-coaters

Fig. 13-5a shows a roller coaster which is raised from ground level to the top of the first tower using mechanical energy. This builds up a reservoir of potential energy in the coaster.

When the coaster is released at the top of the tower, it moves forward and down, the potential energy being quickly converting to kinetic energy and the speed of the coaster increasing accordingly. The speed reaches its maximum when the coaster reaches the lowest point between two adjacent towers. The coaster then moves up to the next tower, the kinetic energy changing back to potential energy, and the speed of the coaster reduces as its potential energy increases. The rest of the towers, dips, twists and turns of the ride, serve to change the energy of the coaster back and forth between potential energy and kinetic energy (Fig. 13-5b).

During the motion, some energy will be lost due to friction and, for this reason, the first tower must be higher than all the other towers so that sufficient energy is provided to overcome the energy loss.