The Physics of Bungee Boarding
Bungee boarding works according to the principle of potential, or stored, energy. In this respect, it's like traditional snowboarding, so it may help to compare the two. With a traditional snowboard, you ride a lift to the top of a hill. The higher you go, the more potential energy you gain by virtue of your position -- gravity wants to pull you back toward where you started. Once you set off barreling down the hill, the potential energy is converted to kinetic energy -- speed -- which powers you for the length of your ride.
In bungee boarding, the cord stores potential energy as it stretches. In this comparison, its elasticity is the equivalent of gravity. When you use the bungee for skateboarding, snowboarding or skimboarding, the friction of your shoes against the ground keeps you from snapping back before the cord is fully stretched. Once you step onto your board, the friction is dramatically reduced and the potential energy in the cord changes to kinetic energy. You accelerate.
When you use the bungee for riverboarding, it's the pressure of the water against the board that helps create the potential energy and keeps the board from snapping back. Held underwater, flat against the current, the board acts like the sail on a boat, absorbing a lot of energy and stretching the cord. When you tilt the board and start riding it along the river surface, the downstream force lessens significantly and the bungee pulls you rapidly upstream.
One essential aspect of using a bungee is the need for an anchor point. You'll have to tie a rope or web strapping that's connected to your bungee around something that won't move, such as a tree. For skimboarding at the beach, it's best to place an anchor out near where the waves are breaking. Most boarders use a Danforth-style anchor with flat flukes that's designed to dig into sand or mud [source: Kalisek].
When using the bungee for anything besides riverboarding, a rider can enlist one or more friends to help create the necessary potential energy. Bungees can be equipped with two handles, allowing the helper to pull along with the boarder. The helper steadies the bungee while the rider mounts the board. When he lets go, the rider takes off.
Now that you're clear on bungee boarding basics, read on for some tips on how to get the most of your experience.