Feb 7, 2009

Physics of ‘the Hit’

TAMPA, Fla. — Isaac Newton’s apple hurt considerably less than Ryan Clark’s coconut. But they did have a few things in common.

Clark’s shockingly violent hit on the Baltimore RavensWillis McGahee two Sundays ago — a full-speed, helmet-to-helmet crash that left McGahee unconscious and Clark all but — didn’t just follow the N.F.L.’s rules, but Newton’s as well. Force equaled mass times acceleration. Momentum was conserved. And the bodies finally came to rest, McGahee’s on a stretcher.

“How I look at it, you can be the hammer or the nail,” the inner scientist in Clark explained this week. “I try to be the hammer.”

The tackle, the art of making the ball carrier not stay in motion, is football’s most primeval action. Amusing physicists the way batting averages do actuaries, collisions lead the highlight reels, impart the force of a deadly car crash, and rely upon kinematics that date to a considerably different big bang.

Sunday’s Super Bowl could very well ride on how well the Steelers’ defense — known as perhaps the most fearsome and bone-clattering in the N.F.L. — can tackle the Arizona Cardinals’ fast and evasive wide receivers. From angles and acceleration to speed and centers of gravity, players might not understand the physics of tackling, but they know how to wield it.

“It’s all about timing and leverage,” Cardinals safety Adrian Wilson said. “Being able to time the hit the right way, and the leverage you’ve got to have once you make impact so the other player goes back, and not you.”

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