Today’s Wonder of the Day was inspired by Ben from , . Ben Wonders, “What is the physics behind different pitches in baseball” Thanks for WONDERing with us, Ben !
It's the bottom of the ninth inning. There are two outs. The bases are loaded. You stand on the mound, staring down your rival's best hitter. You cling to a one-run lead. You wind up and deliver your best fastball. He swings. He misses! Strike one.
The catcher signals for a different pitch: a curveball. You grip the baseball tightly and then whip it toward home plate. It flies toward the batter and then, at the last second, it dips down to avoid the swinging bat. Strike three. You win!
Unlike a fastball, which travels straight to the plate as quickly as possible, a curveball drops and curves as it approaches the batter. Since batters only have a split-second to swing at the ball, they often have trouble hitting curveballs because they can't see them dip and move until it's too late.
How do pitchers throw curveballs? Do they put a hex on the ball? Is it magic? Nope! It's pure science. In fact, all baseball pitches make interesting subjects of study when it comes to learning about the physical laws that apply to the sport of baseball.
For example, physical forces and properties, such as gravity, friction, velocity, acceleration, and momentum, are constantly at work when a ball is thrown and subsequently hit by a bat. When it comes to a curveball, though, the spin put on the ball by the pitcher brings a couple of other scientific principles into play: Bernoulli's principle and the Magnus Effect.
To throw a curveball, a pitcher grips the ball tightly with the middle and index fingers together across the seams of the ball. The middle finger is critical, as the pitcher needs to make sure that the seams provide resistance against the middle finger during the release. This resistance helps the pitcher to put topspin on the ball as it's released with a tight rotation.
When the ball is released, a pitcher hooks his wrist rather than simply flicking the wrist downward as he would when throwing a fastball. As the pitcher hooks his wrist over the ball and to the side, he creates a tight spin that will result in the ball curving and diving as it reaches the plate.
As a curveball flies through the air, the spin creates an imbalance of air pressure on either side of the ball. According to Bernoulli's principle, this imbalance of air pressure creates lift. When applied to a spinning object, the Magnus Effect holds that the force of lift generated will cause the spinning ball to move in the direction of lower pressure.
For a right-handed pitcher, a curveball spins clockwise as it heads toward home plate, pushing through the air, and slowing by the force of friction caused by the resistance of the air. Because of the ball's spin, air will pass more quickly on one side than the other. In other words, the air will move with the spin of the ball on one side and against the spin of the ball on the other side.
The side of the ball where the air passes faster will experience reduced air pressure. The result is that the ball will curve in the direction of lower air pressure. Most of this curvature will occur in the last quarter of the ball's trip to home plate, which explains why curveballs are so hard to hit.
If you're skeptical that a curveball could curve that much or be that hard to hit, consider this: a major-league pitcher can throw a curveball that spins as fast as 30 times per second. During its quick trip to home plate, a curveball could turn over 15 times and curve a distance of over 17 inches!