Baseball Curve Ball

A curve ball is a type of pitch thrown by a baseball pitcher in which the way the ball is gripped and released and the arrangement of stitching on the ball causes additional rotation, which results in the ball traveling in an exaggerated, or curved, flight. When thrown as intended, curve balls curve distinctly as they approach the batter—what is called the curve-ball's break.

Credit for the invention of the curve ball in the late-1800s is generally given to American baseball player William Arthur "Candy" Cummings (1848–1924). The curve ball's first acknowledged public demonstration occurred on August 16, 1870, by major league pitcher Fred Goldsmith (1856–1939). However, for years afterward, baseball fans debated as to whether a curve ball actually curved. The controversy was settled when fast photography (photographs taken in the dark with stroboscopic lighting) was first used in 1941 by researchers associated with Life magazine, who viewed the curve ball's path.

Certain forces act on a baseball regardless of how it is thrown. When a pitcher throws a baseball, the forward movement of the arm propels the ball with a force that produces a velocity. (In the major league, pitchers often throw baseballs in excess of 85 mph [136 km/h].) A countering force called drag (air resistance) slows the ball down. Simultaneously, the force of gravity places a downward motion onto the ball.

In the case of a curve ball, spin (rotation) is added to the ball when the pitcher snaps his or her wrist downward as the ball is released. Because of this action, another force called the Magnus force is able to explain the motion of a curve ball. The Magnus force, named after German physicist Heinrich Gustav Magnus (1802–1870) who described it in 1853, acts on a baseball due to the stitches located on its surface. The spinning of the stitches causes air pressure on one side to be less than the pressure on the opposite side. The ball is compelled to rotate faster on the side with less pressure than on the side of greater pressure. Because of this difference, the ball curves.

When the so-called Magnus effect is used by a pitcher to throw a curve ball, a difference of forces as little as one part in a thousand—when a ball is thrown at 75 mph (120 km/h)—can produce a curve just over 1 ft (0.3 m). A baseball traveling from a right-handed pitcher rotates at about 1,800 revolutions per minute. Thus, on its trip of about 56 ft (17 m) from the mound's edge to the plate, the ball will rotate about 16 times. According to statistics, the ball's surface facing the third base side will rotate at about 85 mph (137 km/h), while the first base side will rotate only at about 55 mph (89 km/h). Drag is greater on the faster rotating side (and less on the slower side) so the ball is deflected toward the first base side—and away from a right-handed hitter. Therefore, a right-handed pitcher has a better chance of striking out a right-handed batter because curve balls will break down and away from the batter, making the ball much more difficult to hit. Likewise, a left-handed pitcher prefers to throw curve balls to left-handed batters.

see also Baseball bat speed; Baseball bats: Sweet spots and tampering.