Why does a curve ball curve?

(Lansing State Journal, April 14, 1993)

Question submitted by T.L.Smythe.

A curve ball is possible because of the Bernoulli principle. The Bernoulli principle says that the faster an air stream is moving the lower the pressure in that air stream is.

When a pitcher throws a curve ball the ball leaves his or her hand spinning. As the ball spins, the air closest to the ball moves along with it. This means that the air on one side of the ball will be moving faster than the air on the opposite side. This also means that on one side of the ball there is a lower air pressure than on the other. The air on the high pressure side of the ball (the slower moving air) pushes on the ball more than the air on the low pressure side (faster moving air). The ball is then pushed to one side as it moves forward and the ball's path curves from the pitcher to the plate.

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