| Why do we "stick" to the earth rather than float | | | | New Jersey park called Action Park. It was only |
| upwards? Because of gravity. Why do we "stick" | | | | open for about a month in 1985 and for only a |
| to the roller coaster cars as they go upside down | | | | few days in 1995, but both times there were |
| in a loop? Because of gravity. It sounds weird, but | | | | enough bloody noses and back injuries that it was |
| it's true. | | | | clear that the ride could not remain open. |
| A roller coaster loop isn't actually circular. It is | | | | To avoid the problems of excessive g forces, |
| more of a teardrop shape that is called "clothoid," | | | | coaster (and water slide) designers make the |
| a spiral in which the radius changes constantly. In | | | | loops in a clothoid shape. The rider feels the |
| a perfectly circular loop the radius is constant. But | | | | greatest speeds at the bottom of the loop, both |
| in a clothoid loop, the radius at the bottom is | | | | entering and exiting. The rider's lowest speed in |
| larger than the radius at the top. It's much the | | | | the loop is at the top of the loop. This way, the |
| same shape as a standard helium balloon. | | | | forces are 3 or 4 g's, which are exciting, but not |
| If a roller coaster loop were circular, to have | | | | dangerous. |
| enough speed to hold the cars to the track as | | | | Another way to look at it is that it is the inertia |
| they loop over would require 8 g's of acceleration | | | | keeping you from falling out of the roller coaster. |
| as you go into the loop. Fighter pilots black out | | | | This is what presses your body to the outside of |
| when they experience 7 or more g's, so this | | | | the loop as the cars go through the loop. Gravity |
| would clearly be dangerous to the human body. | | | | is still pulling you down to the ground, but at the |
| There have been a couple of cases of designers | | | | top of the clothoid loop, the acceleration pulling |
| trying to include perfectly round loops. One was | | | | upward is stronger than gravity. |
| not a coaster, but an enclosed water slide in a | | | | |