The physics of baseball pitching

Baseball is the oldest professional sport in the U.S. It is a game of great subtlety (like cricket!) which has fascinated fans for over a hundred years. It has also fascinated physicists--partly, because many physicists are avid baseball fans, but, partly, also, because there are clearly delineated physics principles at work in this game. Indeed, more books and papers have been written on the physics of baseball than on any other sport.

A baseball is formed by winding yarn around a small sphere of cork. The ball is then covered with two interlocking pieces of white cowhide, which are tightly stitched together. The mass and circumference of a regulation baseball are 5oz and 9in (i.e., about $150\,{\rm g}$ and $23\,{\rm cm}$), respectively. In the major leagues, the ball is pitched a distance of 60 feet 6 inches (i.e., $18.44$m), towards the hitter, at speeds which typically lie in the range 60 to 100 mph (i.e., about 30 to 45 ${\rm m/s}$). As is well-known to baseball fans, there are a surprising variety of different pitches. ``Sliders'' deviate sideways through the air. ``Curveballs'' deviate sideways, but also dip unusually rapidly. Conversely, ``fastballs'' dip unusually slowly. Finally, the mysterious ``knuckleball'' can weave from side to side as it moves towards the hitter. How is all this bizarre behaviour possible? Let us investigate.