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 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.
The track begins with a steep climp, building up potential energy in the coaster car. The rest of the
track's hills, valleys, twists and turns are to change the built-up energy back and forth between
potential energy and kinetic energy. As the train moves, it gradually loses energy to friction until it
reaches the end of the ride.
There are two major types of roller coasters, which are defined by what their tracks are made out
of: wooden and tubular steel. The tracks of wooden roller coasters are a little like traditional
railroad tracks. The metal wheels of the cars roll on a flat metal strip, about 4 to 6 inches across.
This strip is bolted to a running track made out of laminated wood. In most coasters, the car
wheels have the same flanged design as the wheels of a train (the inner part of the wheel has a
wide lip that keeps the car from rolling off the side...