We are now only a few weeks out from the unofficial start to the Major League Baseball season, pitchers and catcher reporting. This day, February 13th, 2018, begins the spring training process that leads up to the start of the season on March 29th. My realization of the nearing call, lead me to think about how many different breaking and off-speed pitches that exist in baseball today. What i discovered is that only two main factors contribute to how pitchers manipulate their throws to be more than just a simple thrown ball. Every curve-ball for example moves based on the position in which the ball lies in the pitchers hand, and the spin applied. Of these two factors, spin seems to have the greatest effect and the most physics tucked away.
The physics of pitching starts by looking at air as the fluid it is and knowing it fallows Bernoulli's law. This states that an increase in the velocity of a fluid decreases its pressure. When a pitcher throws a curve-ball they spin the ball to use this principle to do deceive the batter. A baseball has three axis on which it can spin, X. Y, and Z. Forward spin along the x-axis is known as top spin while backwards spin along the x-axis is what we know as backspin. These two spins carry great effects on balls as they introduce rotation either in the direction or against the direction of travel. As the ball flies through the air, the bumps on a ball cause drag that allows the sin of a ball to change the pitches placement and direction. As the ball spins in either direction it causes a pressure differential on either side of the ball due to Bernoulli's principle. Then combine topspin and backspin with a spin along another axis, it is easy to see how all other pitches are created, simply by some combination of these spins.
This all holds true until we consider the one, rare, odd ball pitch: the knuckle-ball. The knuckle ball has little to no spin on it and thus is considered by some to be a cheap pitch and many are not taught to throw it. Simple thought justifies that it would be simple to hit a ball with no spin since it wont move like previously stated. That's where things get complicated. The knuckle-ball benefits from chaotic fluid dynamics where each imperfection in the balls surface leads to an impact on its flight. Since this is so subtle, it only requires a slight change in the balls path to completely change the balls direction. As a result, the ball wiggles uncontrollably and unpredictably fooling even expert batters.