If were going to talk about the physics of amusement
park rides, then we have to talk about roller
coasters. Roller coasters are known for their thrill
inducing heights and speeds. Let's look at how a
roller coaster works.
Conservation of energy
Roller coasters power themselves through the
conservation of mechanical energy. There are two
types of mechanical energy:
Potential energy: is stored energy,
and is associated with the position of an
object. For a roller coaster, we will consider
gravitational potential energy which is
represented for an object as:
where m represents the
object's mass, g represents the
acceleration due to gravity, and y
represents the height above the ground.
Kinetic energy: is the energy of
motion, and is associated with the speed of an
object, it is represented as
where
m represents the object's mass and v
represents the object's velocity.
Let's look at a roller coaster car starting at
the top of a hill. At this point there is potential
energy, but no kinetic energy since the car isn't
moving. Once the car starts moving down the hill it
gains kinetic energy, and since the total mechanical
energy of the system is conserved, this gain in
kinetic energy results from a loss of potential
energy as the height of the car above the ground
decreases.
As the car goes up a hill, it begins to slow down
due to the force of gravity, which means that the
kinetic energy is decreasing. However since the
roller coaster is going upward that loss of kinetic
energy is being transferred into potential energy.
So the total energy of the system still remains
unchanged. The diagram below illustrates this
concept of conservation of energy where even thought
Kinetic and Potential energies change at different
points, the total energy of the system is constant.
Launching Systems Now
that we have learned how a roller coaster
works, let's look at what allows the roller
coaster to get the initial energy needed to
travel along the ride. Roller coasters used
to be lifted the first hill by a chain
system that was run by a simple motor. But
now many roller coasters use launching
systems to get the roller coaster moving
fast enough to reach the top of the first
hill.
Two types of launching
systems are electromagnetic launchers and
hydraulic launchers.
Electromagnetic Propulsion launchers
Electromagnetic propulsion systems use magnetic
fields to move the roller coaster forward. Two
common types of these are the linear induction motor
(LIM) and the linear synchronous motor (LSM). In a
linear induction motor, stators are imbedded into
the track. Then a current is applied to the stators
creating a moving magnetic field. This induces a
magnetic field in conducting metal attached to the
cars of the roller coaster due to Lenz's law, and
this causes movement of the cars. In the linear
synchronous motor, large magnets are placed under
the cars so movement is caused by the attraction and
repulsion to the synchronized magnetic fields from
the stators.
Hydraulic Launchers
Another type of launching mechanism uses
hydraulics. This system uses hydraulic motors to
power a cable drum connected to a planetary gear
box. The cable drum acts like a fishing wheel. As it
spins, the winding cables causes the catch car, or
sled, connected to the roller coaster cars, to
accelerate rapidly. Then the cars are released from
the sled to continue along the ride.
