Study Gets a Handle on Bat Vibrations

Article excerpt

NORTH America's baseball season has opened and, once again, the "crack" of the bat is heard throughout the land. But there's more to the encounter of bat and ball than appears to the casual eye.

It turns out that the impact can set up vibrations that make the seemingly stiff bat wriggle like a snake. Therein lies the secret of some of baseball's subtle features, including the fact that wooden bats tend to break on the side opposite the impact point.

Physicist Lonnie L. Van Zandt of Purdue University in West Lafayette, Ind., details this in a paper in the American Journal of Physics.

Commenting on his research in a telephone interview, he noted that, after more than a century of use, the baseball bat "is a finely tooled artifact." But that doesn't mean that one can't still learn interesting things about it by looking at it from a physicist's point of view.

A bat has a series of normal modes of vibration that Dr. Van Zandt says "is entirely analogous to the harmonics of ... an organ pipe."

He used a mathematical model in a computer to study these modes for a bat shaped to major league specifications and confirmed his results by experiment with a real bat borrowed from his son. He found that the first 20 such vibrational modes have implications for the game.

Everyone who has swung a baseball bat in earnest knows about the "sweet spot." That's the spot where a direct hit on the ball drives the ball fastest. It's the spot where a hit doesn't make the bat sting one's hands. It's also the spot, more or less, where a hit sets up the least vibrational activity. …

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