New Page 1



A roller coaster is like 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, a roller coaster is moved only by the forces of inertia and gravity. The only exertion of energy occurs at the very beginning of the ride, when the cars are pulled up the first hill, or the "lift hill". The purpose of this first climb is to build up potential energy. The concept of potential energy is: As the coaster gets higher in the air, there is a greater distance gravity can pull it down. The potential energy built-up going up the hill can be released as kinetic energy, energy of motion, as soon as the cars start coasting down the hill.

At the top of the first lift hill (a), there is maximum potential energy because the train is as high as it gets. As the train starts down the hill, the potential energy is converted into kinetic energy -- the train speeds up. At the bottom of the hill (b), there is maximum kinetic energy and little potential energy. The kinetic energy propels the train up the second hill (c), building up the potential-energy level. As the train enters the loop (d), it has a lot of kinetic energy and not much potential energy. The potential-energy level builds as the train speeds to the top of the loop (e), but it is soon converted back to kinetic energy as the train leaves the loop (f).
When the coaster is released at the top of the first hill, gravity takes over, applying a constant downward force on the cars. If the track slopes down, gravity pulls the front of the car toward the ground, so it accelerates. If the track tilts up, gravity applies a downward force on the back of the coaster, so it decelerates.