Diagram of a Roller Coaster
1. The station brakes "A" is released to allow the train to coast down sloping track "B" and to engage with the powered lift mechanism "C - D." There is a drop in potential energy from "A" to "B", so the train acquires enough kinetic energy and momentum to enable it to reach and lock onto the uplift mechanism at "C."
2. At "D", the train is at the highest point of the ride and, therefore, has the greatest amount of potential energy, as a result of the input of mechanical energy expended by the lift mechanism.
3. As the train passes the top of hill "D", it detaches from the lift mechanism and freely accelerates down the first drop, "D - E". Riders in the rear of the ride may experience a downwards-centripetal acceleration as they pass over the curved crest, causing them to feel lighter than their normal weight.
4. When the train falls through "height 2" down the ramp "D - E", the resultant potential energy drop is converted into kinetic energy which accelerates the train.
5. At the bottom of the first drop "E", the track curves upward and the train and riders experience an upwards-centripetal acceleration due to the change in velocities. The resulting positive G force causes the riders to feel heavier than normal.
6. The train rises again to hilltop "F", exchanging potential energy gain for loss of some of the kinetic energy, which was acquired by the fall from "D -E". The speed of the train at "F" is the same as if the train had fallen directly from "D - F".
7. The process repeats as the train rises to "F" and falls to "G".
8. After the rise to "H" there is a 180-degree turnaround "I". The turnaround must be well formed to avoid excessive side forces on the train. The speed at "H" is the same as at "E" because their "drop heights", 2 and 6, are the same. Consequently, the interchange of potential and kinetic energy between "E- F", "F - G" and "G - H" balances out.
9. Point "J" is the lowest point in the ride so in theory it is the fastest point of the ride. The greatest potential energy drop is "D - J" which can be described as Potential Height 4.
10. The train continues through smaller hills, "K" and "L", until it reaches the brakes at "M" and station "A". The friction surface of the brakes stops the train. The train's residual kinetic energy is converted to heat in the brake linings.