# Highs & Lows of Roller Coasters Explained by Expert on Coaster’s 125th Birthday

June 13th of this year marks the 125th anniversary of the first roller coaster at Coney Island, the “Switchback Railway.” The 1884 precursor to the modern roller coaster, the Switchback Railway was an example of a “gravity railroad.”

Roller coasters are a popular topic in introductory physics courses because they provide a real-life example illustrating a basic physics principle, according to Hamilton College Physics Professor Amy Lytle. For example, roller coasters don’t use engines to power the cars as they careen wildly up and down the mountains of tracks. Instead, the train of cars is dragged up an initial “lift hill” using a chain or cable assembly. The cars gain what is called potential energy (meaning “having the potential to fall”) at the top of the hill, and this energy is then converted to kinetic energy, or the energy of motion, as they continue along the track. To a physicist, a roller coaster is a classic example of the law of conservation of energy

Gravity is the force most associated with roller coasters. In fact, LaMarcus Adna Thompson, the designer of the first roller coaster, was known as the “Father of Gravity,” due to his great enthusiasm for new and innovative coasters. Many modern roller coasters have gravity-defying vertical loops, where passengers are momentarily upside-down. This demonstrates another classic problem in physics, involving circular motion. These loops are only safely possible when the cars have a large speed, so that riders are pushed into their seats and avoid falling out of their cars, Lytle explains. These high speeds contribute to a sense of weightlessness (or negative G-forces) when passing over tops of hills and strong G-forces at the bottoms of valleys.

In 1884, customers would climb a platform and board a small train car, which would then coast down and up a series of small hills and valleys. The great popularity of this type of amusement ride led soon the construction of new and more thrilling rides. By the 1920s, the wooden full-circuit roller coaster (like Coney Island’s famous “Cyclone”) could be found in amusement parks all over the country.

Since the 1970s, roller coasters have enjoyed a long revival in popularity. Designers continue to push the limits of what is possible (and safe!) in an effort to satisfy thrill-seekers. Lift hills now reach higher than 400 feet, and top speeds exceed 120 miles per hour. While striving for new and exciting experiences, designers must take into account the maximum G-forces riders can safely and comfortably withstand.

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