Roller Coaster Physics: Safe or Reckless?

Arnaldo López Rivera

The thrill and the excitement of riding roller coasters has been a goal of mine since the first time I rode one. Always searching and keeping my eyes opened to find the next biggest, fastest and most wild roller coaster to ride next. At times I often wondered. What little tweaks make the roller coaster go faster? How did the engineers manage to keep the cars from falling while doing loops? And the short and simple answer is through basic concepts in physics!

These physic concepts are present in various parts of a roller coaster ride, for example free falling when the coaster goes over a hill, or the change in G forces felt while the ride is in motion, or the inversions felt while going on a loop. The most basic of physics involved in a roller coaster ride is the kinetic and potential energy. In kinetic energy the faster the coaster moves, the more kinetic energy it has.    Potential energy can be thought of as stored energy. Consider when you lift a heavy object. To do this, you exert energy. This energy becomes available as potential energy, which can then become kinetic energy when you drop the object. Similarly, the lift motor of a roller coaster exerts energy to lift the ride to the top of the lift hill, energy that will eventually become kinetic energy when the coaster drops. Lifting the train higher gives it more potential energy. This potential energy is converted to kinetic energy when the train drops. The further it drops, the more potential energy that gets converted to kinetic energy. In other words, the coaster picks up speed as it falls. The G forces are measured in terms of what you feel when you are sitting still in the earth's gravitational field. When in that state, you are in a 1-G environment. While riding a roller coaster 1 G represents the force the rider experiences while sitting stationary in the earth's gravitational field. As the acceleration on the rider changes, the G forces will change as well.

The most difficult aspect to understand in coaster physics is the friction present during the ride. Without taking friction into consideration the acceleration and the sum of the kinetic and potential energy in the ride would remain constant. Taking friction into account, this sum will continually decrease throughout the ride. So later in the ride, the train can't climb as high as it could in the beginning. To climb a high hill may require more energy than the coaster has left. Furthermore, at the bottom of hills, the train will tend to go slower at the end of the ride than it did at the beginning, because to go fast also means having a lot of energy. A well-designed coaster can still exert more extreme forces at the end of the ride than at the beginning for instance, by making the turns tighter.

These are some of the general physic concepts involved in a roller coaster ride, however there is still the question of safety to be answered. Are roller coasters safe? For the most part roller coasters are very safe; engineers design the ride taking into consideration that the rider does nothing unusual. If you stand up in a sit-down coaster, the calculations will no longer apply.