Why Curve Balls Curve & Spit Balls are Banned

Ever wonder why a curve ball curves and why hitters have such problems hitting the knuckle ball? Kidzworld looks at the physics behind curves, knucklers and spitters.

Physics of Pitching - The Knuckle Ball

The knuckle ball can drive even the best hitters crazy. A knuckler sometimes travels less than half the speed of a fast ball, but at times, it can be much harder to hit. The knuckle ball is thrown by gripping the ball with your knuckles or fingernails. A good knuckle ball, like the one thrown by Tim Wakefield of the Boston Red Sox, will travel slowly and only spin one or two times on its way to the plate. Because the ball isn't moving very fast, the air is able to pass over the stitches of the ball and cause the ball to move up and down or from side to side. A knuckle ball thrown properly will move back and forth on its way to the plate which can often make a good hitter look very foolish when his swing is nowhere near the ball.

Physics of Pitching - The Spit Ball

The spit ball is one of the hardest to hit and can actually be quite deadly. The spit ball was offically banned from baseball in 1920 after Carl Mays threw a spit ball which hit Ray Chapman on the head and killed him. A spitball is any kind of pitch where the pitcher slops some sort of goo - like spit, ear wax, snot or even peanut butter - on the ball before he throws it. Depending on where and how much "spit" a pitcher puts on it, the ball will move wildly up, down, or diagonally - making it extremely difficult for a hitter to see the ball or hit it. Spit balls are banned now, so you won't find yourself trying to hit one, unless the pitcher is cheating!

Physics of Pitching - The Curve Ball

When pitchers throw a curve ball, they put a twist on it at the last moment that causes the ball to spin diagonally or from side to side - rather than a straight backspin like a fastball. That last second spin causes the air around the ball to travel faster at the bottom of the ball's surface than it does at the top. Because it's going faster on the bottom, the ball will suddenly veer downwards, just before it gets to the batter. A batter only has about one fifth of a second to swing the bat, so when the ball changes direction at the last second, it makes it extremely difficult to make contact.

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