Fly Like A Hawk - skateboarder Tony Hawk - Brief Article

Science World, Feb 12, 2001 by Nicole Dyer

Skateboard legend Tony Hawk uses physics to land his daredevil skate stunts.

It had never been done before. Not even Tony Hawk, perhaps the world's greatest skateboarder, had ever landed a front-side "900"--two-and-one-half midair somersaults (900 degrees of rotation)!--the pinnacle of all of skate stunts. Hawk, 33, wrestled with the stunt for 10 years--with nothing to show for it but a busted rib.

Then he headlined the 1999 ESPN X Games, the Olympic Games of extreme sports, where 8,000 screaming fans overflowed Mission Bay Park in San Francisco, Calif.

All eyes were riveted on the lanky skate champ as he launched 1.5 meters (5 feet) off the rim of a half pipe--a hollow U-shaped ramp that's flat in the middle and curls skyward with steep walls. Midair he executed two-and-one-half warp-speed flips with the board tight at his feet. He flawlessly sailed back into the half pipe--and became the first skater in history to nail a perfect 900! The crowd went wild. "It was my greatest personal achievement," says Hawk.

"TRICK" PHYSICS

The most awesome force in skateboarding is gravity, the force that pulls all things toward Earth. Gravity helps keep Hawk glued to his board and guarantees every air-bound trick returns to Earth. Gravity also helps him accelerate, or pick up speed, as he swoops down into the half pipe. Speed is critical for Hawk: the faster he goes, the higher he can soar out of the pipe--and the more seconds for his in-flight magic.

What's the first step Hawk must take to gain speed? Overcome inertia, the resistance of an object to a change in motion. According to Newton's first law of motion, an object at rest remains at rest unless acted upon by an outside force. That means Hawk needs to exert enough force to launch his body and board off the pipe's lip or edge. His leg muscles generate the force in the form of kinetic energy (energy of a moving object).

Another way Hawk amps up speed: a technique called pumping. As he glides across the ramp's flat bottom, called the transition, Hawk crouches low on his board. Then, as he nears the steep incline, he quickly bends his knees and straightens his legs. This raises Hawk's center of mass, the point where he perfectly balances the entire weight of his body, and increases his kinetic energy. More energy translates into lightning-speed maneuvers.

TWIST AND SHOUT

The 900 may be Hawk's ultimate claim to fame: "I thought up the trick in 1986, but didn't have the guts to try it for 10 years." To master the stunt, Hawk endlessly practiced midair somersaults--which rely on angular momentum, or the moving power of a rotating object. At 1.5 m (5 ft) above the half pipe rim, Hawk has less than 2 seconds to complete two-and-one-half full flips. Rotating his legs beneath him--as his arms and torso rotate in the opposite direction--Hawk curls his body into a tight ball. He draws his weight closer to his axis of rotation (center point at which Hawk rotates), and hikes up his speed. It's the same principle used by twirling figure skaters when they perform their routines by pulling their arms close to their body. "The most dangerous thing to do is to panic and stop your spin in the middle of a trick," Hawk cautions. "You end up on your back!"

Naturally, what goes up must come down. The second part of Newton's first law of motion states that objects in motion stay in motion until acted on by an outside force. Hawk might soar skyward forever if not for gravity exerting a downward force on his body and board. Gravity's force reconnects Hawk and his board to the ramp.

Grasping the laws of physics may help you become a better skater, but Hawk also suggests using the laws of common sense. "When I try a trick I don't throw caution to the wind," he says. "I figure out the safest way to approach it, then practice until I can say, 'OK, this is the right way to do it.'"

Hawk officially retired from pro skating last year, but his skate career, along with his skateboard company and best-selling videogame (see "Tony Hawk's Pro Skater 2[TM]), has netted the legend more than $1 million! To join Tony Hawk's fan club, check out his Web site:

www.clubtonyhawk.com

SKATEBOARD LEGEND TONY HAWK rockets off the half pipe to execute what he calls the "Stale Fish"--a midair front-of-the-board grab with one hand. The stunt is one of more than 100 daredevil tricks he's invented. Others include the "Madonna" (Hawk grabs the nose of his board in midair and kicks one leg out) and the "720 McHawk" (in midair Hawk flips twice with the board at his feet).

How does he do it? Practice! The California native started skateboarding at age 9. By 14, he ranked as the world's number one boarder and since then has nabbed more prizes than anyone. "Skateboarding keeps me motivated," Hawk says. "Every time I get on the board I learn something new."

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GRAVITY "DROPS IN"

1 Hawk drops into the half pipe by pushing off its solid rim. In turn, the rim pushes back on Hawk with an equal and opposite force to propel him forward. (The same force rebounds a tennis ball as it smashes against a wall).