Physics of Roller Coasters

Roller coasters are driven almost entirely by inertial, gravitational and centripetal forces. Amusement parks keep building faster and more complex roller coasters, but the fundamental principles at work remain the same.

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 relea...

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...ly upside down, gravity is pulling you out of your seat,

toward the ground, but the stronger acceleration force is pushing you into your seat, toward the sky.

Since the two forces pushing you in opposite directions are nearly equal, your body feels very light.

As in the sharp descent, you are almost weightless for the brief moment when you are at the top of

the loop. As you come out of the loop and level out, you become heavy again. In a loop-the-loop,

the intensity of the acceleration force is determined by two factors: the speed of the train and the

angle of the turn. As the train enters the loop, it has maximum kinetic energy -- that is, it is moving

at top speed. At the top of the loop, gravity has slowed the train down somewhat, so it has more

potential energy and less kinetic energy -- it is moving at reduced speed.