Ferris Wheel Physics

There is no better place to see physics at work than an amusement park. Whether it’s the winding roller coasters or tricky and nearly impossible games, physics is present in all of it. If you have ever been on a Ferris Wheel you have experienced, first hand, physics at work. In class we have encountered acceleration and x,y and vector components many times and all of these concepts are seen in the physics behind the Ferris Wheel.

The Branson Ferris Wheel in Missouri

Ferris wheels rotate on a central axis and consist of an upright wheel with seats attached at the rim. These seats (gondolas) can pivot freely at the support where they are connected to the Ferris Wheel, which is why they always hang downwards. Ferris Wheels spin in an upwards motion with the help of gears and motors, and the wheel comes back down again due to gravity. This cycle of circling up and down happens simultaneously during the ride.  

Many people wonder, why is it you feel lighter at the top of the Ferris Wheel and heavier at the bottom? After all, your mass doesn't actually change at different points throughout the ride, so how can that be? Before we can answer this question, the following video will give us some necessary basic information.

To sum it up: Centripetal acceleration is the acceleration of an object moving in uniform circular motion, resulting from a net external force; centripetal means “toward the center” or “center seeking”. In this case it is important to remember centripetal acceleration is always pointing to the center of the ferris wheel. Another important factor to consider is angular velocity. This is the rate of change of this angle with respect to time.

Most of the time, a Ferris Wheel will rotate at a constant speed, unless slowing down to let passengers off, but velocity is constantly changing because the direction is different every second. Passengers feel their “true weight” at the bottom because the centripetal acceleration is pointing horizontally and has no vector component parallel with gravity. When the passenger is exactly halfway between the top and bottom, there is no contribution in the vertical direction. At these two positions, centripetal acceleration presents a vector parallel with gravity, so they can be directly added together.

However, at the top of the ferris wheel, centripetal acceleration is pointing directly down. The force being exerted on the passengers is F1, where F1 = m(g-a). Standing on earth we are at 1g, and at the top of the ferris wheel the passengers usually experience 0.5g, causing them to feel lighter. Whereas at the bottom of the ferris wheel, both rotation and weight forces combine resulting in greater g force (acceleration), causing the passenger to feel heavier. At the bottom, centripetal acceleration is pointing directly up, and the passengers experience 1.5g, causing them to feel heavier.

Those are only a few of the forces at work on a ferris wheel, but next time you’re on a ferris wheel you should know a little bit more about how it works.

Sources

1. “Ferris Wheel Physics.” Observation Wheel Directory, 2016, www.observationwheeldirectory.com/ferriswheelarticles/ferris-wheel-physics/.

2. “Ferris Wheel Physics.” Real World Physics Problems, www.real-world-physics-problems.com/ferris-wheel-physics.html.