Sproiiing!

It's not your parents' pogo stick. It's called a Flybar, and this revamped cousin of the pogo was designed with extreme heights in mind.

Designed by Andy MacDonald, an eight-time World Cup skateboarding champion, and Bruce Middleton, a physicist from Massachusetts Institute of Technology, the Flybar can bounce over 1.8 meters (6 feet) into the air. Unlike its wimpy relative, the Flybar can support the weight of an adult. And it feels more like bouncing on a trampoline than jumping on an old, springy mattress.

A traditional pogo stick's jumping power comes from a steel spring inside its body. When you jump onto the pogo's pedals, the force (push or pull) of your weight pushes the body of the pogo stick toward the ground. That stretches a metal spring that's attached to both the top of the stick and the foot pegs. As the spring's coils elongate, the pogo gains elastic potential energy, stored energy due to being stretched or compressed. When the coils are stretched to their max, your knees pull up. Then, BOING! The spring quickly returns to its original length. All of that stored energy is released to the rest of the pogo stick in the form of work (transfer of energy). The result: The rider bounces off the ground.

Because steel is not very elastic (stretchy), a large spring is needed to pack high-flying energy. The trade off: Steel is heavy. And the extra weight keeps large-spring pogo sticks closer to the ground.

Enter the Flybar. The secret to this toy's high bounce and trampolinelike feel are the 12 elastomer (rubber) springs inside its body. When a rider pushes down on the Flybar's foot pegs, the elastomer springs stretch like giant rubber bands. These rubberry springs are lighter and much more elastic than a traditional pogo stick's steel spring. So the Flybar stores about four times the amount of elastic potential energy as the low-going pogo can. And this additional energy propels the rider high into the sky. "I've seen people bounce 2 meters (6.5 feet) off the ground," says Middleton. That's four times the bounce-height of a pogo stick.

With more air time, riders can twist, turn, and test new stunts. "It's just fun," says David Jargowsky, Flybar project coordinator. This air-bound apparatus is attracting athletes both young and old who are looking for a new thrill with a twist.

Did You Know?

* As a straight rod, steel is so strong that it doesn't stretch or bend easily. However, when it is coiled, the tiny bends in each segment allow the steel piece to become springy.

* In 1990, Gary Stewart from Huntington Beach, California, jumped 177,737 times in a row on a pogo stick. This worldrecord feat took more than 20 hours.

Resources

* To see pictures and watch videos of people using the Flybar, go to: www.flybar.com/pages/index.html

* To learn about the different forms of energy, go to: www.physicsclassroom.com/Class/energy/energtoc.html

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