In baseball, how does a pitcher throw a curveball?
A successful major league batter gets a hit only 30 percent of the time he
comes to bat. One of the ways pitchers lower these chances even further is by
throwing a curveball. A curveball is a pitch that appears to be moving
straight toward home plate but that is actually moving down and to the right
or left by several inches. Obviously, a pitch that curves is going to be
harder to hit than a fastball that is moving straight.
There are two basic factors involved in creating a curveball:
Any baseball pitch begins with how the pitcher grips the ball. To throw a
curveball, a pitcher must hold the baseball between his thumb and his index
and middle fingers, with the middle finger resting on the baseball seam. When
the pitcher comes through his motion to throw the ball, he snaps his wrist
downward as he releases the ball, which gives the ball topspin. If the pitcher
throws properly, the back of his hand will be facing the batter at the end of
the motion. The ball will break down and away from a right-handed batter if
thrown by a right-handed pitcher.
The spinning action created when the pitcher releases the ball is the secret
behind the curveball. This spinning causes air to flow differently over the
top of the ball than it does under the ball. The top of the ball is spinning
directly into air and the bottom of the ball is spinning with the air flow.
The air under the ball is flowing faster than air on top of the ball creating
less pressure, which forces the ball to move down or curve. This imbalance of
force is called the Magnus Effect, named for physicist Gustav Magnus, who
discovered in 1852 that a spinning object traveling through liquid is forced
to move sideways.
Adding to the air pressure exerted on the ball are the 108 red stitches that
hold the cover on the ball. Because they are raised, the stitches increase the
amount of friction created as the air passes around the ball and places more
air pressure on top of the ball. A well thrown curveball can move as much as
17 inches either way. If you've ever seen a batter jump out of the way of a
baseball that ends up crossing over the plate, you've seen a good curveball.