Question Why don't I fall out when a roller coaster goes upside down?

Answer

Gravity is counteracted by centripetal force, due to acceleration, which is the force that pushes you into your seat.

Have you ever wondered how roller coasters stay on their tracks and why people can hang upside down in them? It’s all a matter of physics: energy, inertia, and gravity.

A roller coaster does not have an engine to generate energy. The climb up the first hill is accomplished by a lift or cable that pulls the train up. This builds up a supply of potential energy that will be used to go down the hill as the train is pulled by gravity. Then, all of that stored energy is released as kinetic energy which is what will get the train to go up the next hill. So, as the train travels up and down hills, its motion is constantly shifting between potential and kinetic energy.

The higher the hill the coaster is coming down, the more kinetic energy is available to push the cars up the next hill, and the faster the train will go. Plus, according to Newton’s First Law of Motion, “an object in motion tends to stay in motion, unless another force acts against it.” Wind resistance or the wheels along the track are forces that work to slow down the train. So toward the end of the ride, the hills tend to be lower because the coaster has less energy to get up them.

The two major types of roller coasters are wooden and steel. Features in the wheel design prevent the cars from flipping off the track. Wooden tracks are more inflexible than steel, so usually don’t have such complex loops that might flip passengers upside down.

In the 1950s tubular steel tracks were introduced. The train’s nylon or polyurethane wheels run along the top, bottom, and side of the tube, securing the train to the track while it travels through intricate loops and twists.

When you go around a turn, you feel pushed against the outside of the car. This force is centripetal force and helps keep you in your seat.

In the loop-the-loop upside down design, it’s inertia that keeps you in your seat. Inertia is the force that presses your body to the outside of the loop as the train spins around. Although gravity is pulling you toward the earth, at the very top the acceleration force is stronger than gravity and is pulling upwards, thus counteracting gravity. The loop, however, must be elliptical, rather than a perfect circle, otherwise the centripetal force would be too strong for safety and comfort.

How do we know whether a roller coaster is safe? Engineers and designers follow industry standards and guidelines. The first “riders” are sandbags or dummies. Then engineers and park workers get to try it out. Would you want to be one of the first passengers on a new ride?

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