Ask a Scientist/Subject Librarian: THIS IS HOW WE ROLL

Asked by:  Nicholas Catarella
School: Glenwood Elementary School, Vestal
Grade: 1
Teacher: Miss Brigham
Hobbies/Interests: Riding roller coasters and water slides, playing hockey
Career Interest: Engineer that designs roller coasters

 Answered by:  Lee A. Cummings
Subject Librarian for Engineering, Binghamton University
Research area: Information literacy, library collections and Reference Services 
Hobbies/Interests: Reading, Pop Culture, Martial Arts 
If you’ve been to Disneyland, Busch Gardens or a Six Flags theme park (or even if you’ve just seen their commercials on TV), then you know how impressive roller coasters can be. They can be hundreds of feet tall, taller even than the tallest building in downtown Binghamton. And they can reach speeds well over 100 miles per hour. They may seem scary, but they are very safe and can be lots of fun.

Roller coasters make a lot of different motions. They drop, and turn, and lift, and loop. The motions of most roller coasters is dependent almost entirely on gravity, the force that gives us weight and allows things to stay firmly planted on the ground and not float off into space. In order to take advantage of gravitational forces, a train of roller coaster cars must first reach an appropriate height to build up the right amount of potential energy, or “stored-up” energy. This is accomplished by using a chain mechanism to lift the train to the top of the first hill. A motor drives a rolling chain called a “chain lift”, which looks like a lot like a giant bicycle chain, with many links and connections. The chain runs beneath the first hill in a roller coaster, and under each car in the train is a piece of metal called a “chain dog.” The chain dog catches onto the chain lift, and the mechanical motion pulls the train up to the top of the hill, where the chain dogs finally let go, allowing the train to rush down the first hill.
Once the train makes it down the first hill, its momentum – the energy built up from speeding down the first hill – keeps it moving forward. The train is able to make loops and corkscrews thanks to this momentum. Loops and corkscrews on a roller coaster are designed by engineers as part of the entire construction of the track. Roller coaster tracks are built in sections (straight and curved), and then welded and bolted into one long track at the amusement park. Safety wheels attached to each of the cars keep them on the track as they make loops. The train’s momentum carries it through the entire loop, or series of loops and corkscrews. And centripetal force, the force that keeps objects moving in a circular path, keeps the riders pressed safely into their seats during the loop. Of course, safety restraints, like belts and over-shoulder bars, are there to provide extra support for every rider.
After all of the drops and loops in a roller coaster are made, a section of track much lower than the first drop helps the train of cars to slow down. The roller coaster operators then use brakes to bring the ride to a stop.
 
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