The Physics of Pitching in Softball

When a player learns the proper mechanics of softball pitching, she’s really taking a physics lesson. Physicists can have a field day watching a softball pitcher and explaining how she uses force to accelerate the ball and how external forces act on the ball after she releases a pitch. You don’t have to know physics to pitch well, but understanding the principles helps ensure that your coach’s instructions make sense.

Windmill Power

In physics, an object’s kinetic energy is equal to work multiplied by displacement. In softball terms, a pitch’s velocity equals the force applied by the pitcher times the distance the ball travels before release. This explains why softball pitchers use a long, windmill wind up. By moving the ball in a circle, it travels a greater distance than if the pitcher moved the ball straight back and then straight ahead. During a windmill wind up, the ball accelerates until it leaves the pitcher’s hand, after which, gravity and wind resistance begin to reduce its velocity.

Use the Force

A softball pitcher does several things to add force to her delivery and, thereby, increase the speed of her pitches. First, she rocks back a bit before moving forward. The forward weight shift adds momentum to the start of her delivery. She also steps forward toward the plate, pushes off the mound with her back foot and snaps her wrist while releasing the ball. All these forward motions add force and help the ball accelerate throughout the wind up, reaching a peak velocity at the delivery point.

On the Rise

The rising fastball, or riseball, is a key pitch for many softball hurlers. The pitch is thrown with backspin -- the top of the ball rotates toward the pitcher -- and with a low-to-high trajectory. The ball’s backspin lowers the air pressure above the ball, leaving the air pressure higher below the ball, which has a lifting effect. Although a typical pitcher’s riseball doesn’t actually rise higher than its initial trajectory, the lifting effect prevents it from dropping as much as it would if it weren’t spinning. Depending on the ball’s weight, however, a riseball thrown with sufficient velocity could actually rise above its initial trajectory.

Throwing a Curve

A softball’s laces create turbulence in the air. As a result, some air remains near the ball longer than it would if the ball were smooth, and the turbulence reduces drag. When pitchers throw curve balls, drag is reduced on one side of the ball more than the other, causing it to bend toward the side of less drag. For example, when a right-handed pitcher throws a standard curve ball, she spins the ball so its left side rotates toward her as the pitch travels to the plate. This results in less air pressure on the ball’s left side, so it curves to the pitcher’s left and away from a right-handed hitter.