Notes

Roller coasters have a long, fascinating history. The direct ancestors of roller coast­ers were monumental ice slides -- long, steep wooden­ slides covered in ice, some as high as 70 feet -- that were popular in Russia in the 16th and 17th centuries. Riders shot down the slope in sleds made out of wood or blocks of ice, crash-landing in a sand pile.

Coaster historians diverge on the exact evolution of these ice slides into actual rolling carts. The most widespread account is that a few entrepreneurial Frenchmen imported the ice slide idea to France. The warmer climate of France tended to melt the ice, so the French started building waxed slides instead, eventually adding wheels to the sleds. In 1817, the Russes a Belleville (Russian Mountains of Belleville) became the first roller coaster where the train was attached to the track (in this case, the train axle fit into a carved groove). The French continued to expand on this idea, coming up with more complex track layouts, with multiple cars and all sorts of twists and turns.At first glance, a roller coaster is something like a passenger train. It consists of a series of connected cars that move on tracks. But unlike a passenger train, a roller coaster has no engine or power source of its own. For most of the ride, the train is moved by gravity and momentum. To build up this momentum, you need to get the train to the top of the first hill (the lift hill) or give it a powerful launch.The world's tallest and fastest roller coaster, the Kingda Ka at Six Flags Great Adventure in New Jersey.
The world's tallest and fastest roller coaster, the Kingda Ka at Six Flags Great Adventure in New Jersey.Roller Coaster Physics
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The purpose of the coaster's initial ascent is to build up a sort of reservoir of potential energy. The concept of potential energy, often referred to as energy of position, is very simple: As the coaster gets higher in the air, gravity can pull it down a greater distance. You experience this phenomenon all the time -- think about driving your car, riding your bike or pulling your sled to the top of a big hill. The potential energy you build going up the hill can be released as kinetic energy -- the energy of motion that takes you down the hill.

Once you start cruising down that first hill, gravity takes over and all the built-up potential e­nergy changes to kinetic energy. Gravity applies a constant downward force on the cars.