The reason you don’t fall out of a roller coaster — even when it’s upside-down

Many kids — and adults — might wonder how a roller coaster stays on its tracks on an upside-down loop or why coaster riders feel like they might fly out of their seats at the top of a big hill.

The answers can be found in physics.

How roller coasters work can be explained by the law of conservation of energy, which says energy can’t be lost or created, only transferred from one form to another. When coaster cars go up the hill and top the crest, they have their highest gravitational potential energy. As the car goes down the hill, that potential energy becomes kinetic energy. That energy is transferred again and again throughout the ride.

The first hill of a roller-coaster ride is always the biggest, and the potential energy generated by the big drop is what powers the rest of the ride, according to a 2015 article in Scientific American. If the coaster creator tried to put another equally-tall or taller hill in the middle of the ride, the cars might roll back down the way they came.

Roller coaster cars need enough speed to make it through loops. The minimum speed they need is called the critical velocity and has a mathematical computation coaster designers must follow to make a successful ride. As a safety precaution, most coasters have wheels on both sides of the tracks to keep the cars from falling.

While it looks like a roller coaster’s loops are round, they are actually teardrop shaped to reduce the force on riders at the bottom of the loops.

This bring us to gravitational force, or G-force.

Humans are used to feeling 1 g, which is the force applied by gravity while standing on Earth at sea level. But when a roller coaster crests the top of a big hill, the acceleration is subtracted from 1 g and we feel zero g or negative g. Even though the gravitational force isn’t really changing, the coaster rider feel weightless, or as if they were flying out of the car. Gravitational force adds to the g’s at the bottom of a hill, possibly increasing to 2, 3 or more.

Coasterpedia.net reported in 2019 the roller coaster with the highest g forces was Tower of Terror at Gold Reef City in South Africa. That ride has a G-force of 6.3!

Comments: erin.jordan@thegazette.com, (319) 339-3157