Stadium Dugout Announcer's Booth Batting Cage Bullpen Behind the Plate

The Curveball

McCovey swings and misses, and it's fouled back.
- Jerry Coleman, announcer and former New York Yankees second baseman

I. Why Does a Curveball Curve?

The game of baseball is played out as duel between the pitcher and the batter. The pitcher will try to throw a ball so that the batter doesn't hit it. How does the pitcher accomplish this?

The pitcher has to throw the ball inside a target of 20"x23"x17" box such that even if the hitter hits the ball, he won't be able get a clear hit. To achieve that goal, the pitcher uses various pitches, such as the curveball, sinker, slider, or fastball.

So how does the pitcher throw these pitches? Well, it is all in the grip. Before we go into which grips to use lets first examine why these grips work.

As the pitcher releases the ball, the grip will put a spin on the ball. When the ball moves through air, it encounters a force called drag. What is drag? Drag is another name for air friction.

If a ball is not spinning, air friction will only slow it down. However, for a baseball at least, when it is spinning, the force of drag will be different at all points: it is less on one side of the ball. This imbalance of force causes the ball to "curve."

Another factor also help the baseballs to curve: its roughness. Balls looks smooth enough you may say. Well, baseball cannot be considered a smooth: they have stitches, in fact, there are 108 of them on every ball. These stitches contribute to the imbalance of the drag. If the baseball was "perfectly" smooth, none of the special pitches of baseball, like the curveball or slider, would be possible. But because of the stitches, the spin of these pitches will cause them to curve.

But wait some say, fastballs spin and they do not curve! However, most baseball players know that fastballs DO curve. In fact, a 90 mile-per-hour fastball will "hop" as much as 4 inches! Well, what is meant by "hopping" is that the ball will stay longer in the air than a normal throw.

So how should you grip the ball to throw a particular pitch? Try this lesson

Want to learn more about the physics behind a curveball? Go to this lesson