Steven Mainzer and Luke Brown
Magnetics play a big part in providing loops for extra fun!
Roller Coaster
Roller Coaster
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Pictured above is a magnetic braking device used in order to stop the coaster.
Magnetism plays a very important role in the way roller coasters function. Their primary use is to launch and stop the coaster, or in other words accelerate or deccelerate the carts on the track. The quick launch of a roller coaster is often due to magnetic propulsion or in simpler terms magnetic "launching."Therefore, the magnets repel each other by using like poles instead of opposite. Using this method of magnetic propulsion, roller coasters can reach a speed of up to 100 miles per hour within seconds. In order for the roller coaster to come to an abrupt hault or slow down smoothly the magnets attract each other and use opposite poles to do so.

The most efficient way to create acceleration within a roller coaster is with strong magnets and opposite poles. When one pole or charged side of a magnet comes close to another same charge pole, they push away from each other or repel. This is exactly what happens in rollercoasters, with one certain pole on the rollercoaster car, and another magnet pole with the same charge on the track. Once the track magnet is put near the cart, the cart repels. Since these magnets are very strong, they repel with great force, causing the cart to accelerate away from the initial point on the track.
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The magnets are fixed on the bottom of the cart providing a safe ride.

Just like in acceleration, the rollercoaster also relies on strong magnets to decelerate and brake. The magnets that are on the cart still hold a certain positive or negative charge, with one of those facing away from the cart. There are magnets at the end of the track but these magnets hold the same charge as the magnet on the cart. When the cart begins to roll over these track magnets with great speed, the two strong magnets immediatly attract each other, slowing the cart down. This is how the magnets are used to decelerate the rollercoaster.
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We just thought this picture was awesome.
As stated above, the magnetic braking propulsion and braking systems are the primary ideas behind the physics of roller coasters. In order for a roller coaster to function an automated system must control and time the sequences in which the magnets react. This way there is no error in the timing of when the magnets are used, and create a perfect stop or let the coaster accelerate at a reasonable rate. The charges on the magnets play a part in the propulsion process because they have to be the same charge in order for the launch to be successful. Same goes with the braking system except the charges must be opposite for the stoppage to work.
We were unable to upload the video on the page so here's the link.
Here's a video that represents how not only magnets relate to roller coasters.