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SPIN MASTER


(From the October 22, 2007 issue of Science World.)

A teen masters the ups and downs of yo-yos, putting a cool new spin on an old toy

Fourteen-year-old Washington State yo-yo champion Sterling Quinn can juggle two yo-yos on one string, send his yo-yo zinging across his body, and weave webs of string so complicated you loose count of all the yo-yo's flips and turns. Yo-yos have been around for thousands of years, but only recently have yo-yoers, like Sterling, been able to pull off such jaw-dropping tricks.

With the help of high-tech yo-yos designed to work with the laws of physics, Sterling and a new generation of yo-yoers are turning an ancient game into an extreme sport.

Learning the Ropes

Sterling started toying around with yo-yos in 2004, but it wasn't until he watched the first annual Pacific Northwest Yo-Yo Championship in Seattle that he was officially hooked. Sterling was mesmerized by the tricks performed by the competitors. “I saw how amazing they were and wanted to be that good,” he says.

Sterling joined a local yo-yoing club, called Strung Out, where the older members guided him through tricks. A few years later Sterling was beating these long-time yo-yoers at their own game.

Sterling now knows more than a hundred tricks. But before he ever attempted stunts with names like Split the Atom, Double or Nothings, and Lacerations, he had to learn a fundamental part of all yo-yo moves—getting his yo-yo to “sleep.”

Sound Asleep

To get his yo-yo to sleep, or remain spinning at the bottom of its string, Sterling quickly throws down his yo-yo. As it falls, the string that's looped around the toy's axle begins to unwind, causing the yo-yo to rotate. Since the yo-yo is moving in a downward line, it builds up linear momentum (an object's mass times its velocity); but it also gains angular momentum, or momentum from rotating. It's this angular momentum that causes the yo-yo to sleep.

Sterling gets the yo-yo to wind back up by jerking his hand upward. This action briefly adds slack to the string, allowing it to rub against the spinning yo-yo. Friction, a force of resistance, between the string and the axle causes them to grip and the spinning yo-yo rewinds up the string.

Pulling off a difficult yo-yo trick requires Sterling to keep his yo-yo sleeping throughout the entire maneuver, even while it's whirling through the air or cradled in a net of string. If the yo-yo stops spinning, it won't have enough energy to zip back up to his hand so he can launch into the next stunt.

Tricked Out

Competition yo-yos, like Sterling's, have been redesigned to maximize their ability to snooze. Getting a yo-yo to sleep longer gives yo-yoers time to complete wilder tricks than ever before.

Toy engineers' first improvement was to make yo-yos heavier by attaching metal edges. Newton's first law of motion states that all objects have inertia, or resistance to change in motion. As an object's mass increases, so does its inertia. The increased weight makes it hard to stop the yo-yo once it starts spinning, explains Sterling.

New yo-yos also have ball bearings—a metal wheel containing steel spheres—fitted around their axles. When a yo-yo spins, the outside of the bearing rolls smoothly over the balls. “The ball bearings reduce friction,” says Sterling. That means the slick bearing won't grab onto the string as easily, so the yo-yo can continue sleeping for minutes at a time.

Yo-Pros

Yo-yos now sleep so soundly a tug is not enough to get the spinning orb to return to a player's hand. To wake up their toys, professional yo-yoers attach a ring of rubbery or textured material to the inside walls of their yo-yos, says Sterling. The material helps snag the yo-yo's string when they yank, so it returns to the palm of their hand.

At yo-yo contests, Sterling's competitors usually range from 12 to 25 years old. Everyone gets three minutes to show off a routine of tricks that will win the most technical and performance points from the judges. Sterling likes to time his tricks to alternative rock music to get the best effect.

Why are kids like Sterling getting into yo-yoing? “You can do it anywhere, and it's fun by yourself or with a group of people,” says Sterling. And unlike another of his hobbies, skateboarding, you're less likely to get hurt. Unless you count string burn on your fingers, he jokes.

—Cody Crane

Check out the National Yo-Yo Museum the worlds largest public display of yo-yos and yo-yo memorabilia.