The same principle that allow curveballs to curve also allow airplanes to fly. This is proven by something called Bernoulli’s principle: Airplane wings are designed to be curved on top, which creates an imbalance of air pressure on either side of the wing, resulting in lift.

When pitching a curveball, the pitcher puts a spin on the ball when releasing it from his hand. As it travels through the air, the spin causes the ball to disturb the air around it.

However, the spin causes air on one side of the ball to move faster than the other, resulting in uneven pressure on the ball, making it curve. A related scientific principle, the Magnus Effect, forces the spinning ball to move in the direction of lower pressure. Then, the baseball’s raised seams help guide the ball by creating airflow resistance.

The amount of break on the ball depends on how hard the pitcher can snap the throw off, or how much forward spin can be put on the ball. The harder the snap, the more the pitch will break. Curveballs primarily break downwards, but can also break toward the pitcher’s off hand to varying degrees. Unlike the fastball, the height of the ball’s flight path arc does not necessarily need to occur at the pitcher’s release point, and often peaks shortly afterwards. Curveballs are thrown with considerably less velocity than fastballs, because of both the unnatural delivery of the ball and the general rule that pitches thrown with less velocity will break more.

An excellent explanation is given in “The New York Times Book of Science Literacy.” “The ordinary curveball, breaking to the left or the right, relies on a lateral force caused by its rapid spin. The sideways spin lowers the pressure on one side and raises it on the other. The effect of spin is potent. A ball spinning at 1,800 revolutions per minute a ball that will turn about 15 times in its 60-foot, 6-inch journey to the plate will feel a sideways force of more than an ounce, which will turn its path by about one and a half feet.” 
So, a curveball curves because the pitcher has enough skill to use scientific principles for his own benefit.

Reference:

“Curveball Science.” Astrocamp School, 29 Aug. 2016, astrocampschool.org/curveball/.

After leaving a pitcher’s hand, a baseball pitch is influenced by three forces: gravity, drag, and the Magnus force. Gravity pulls the ball downwards, drag slows the ball down, and the Magnus force generates a perpendicular force, depending on what pitch is thrown thought. As the ball spins it’s flight path, pressure acts form on it and the Magnus effect generates a force perpendicular to the motion of the ball in the direction of the spin.  In baseball, a pitcher has more control over the spin of the ball than in any other sport. A pitcher can spin the ball to add topspin, backspin, or even sidespin depending on the pitch they want to throw.

Fastballs are the easiest pitches to throw as they are only affected by the Magnus force. A four-seam fastball is a pitcher’s main pitch, which is thrown the most often. There is a tendency to add backspin to the ball as it is released. The backspin points the Magnus force up, causing the ball to fall slower than other pitches, this will create the illusion that the ball is rising. Other fastballs, like the two-seam and the cutter, are thrown with spin, but are moving too fast for the Magnus effect to change their position drastically.

Breaking balls are the pitches that most rely on the Magnus force to be effective. 
As the pitcher releases the ball, he snaps his wrist over the ball, putting a huge amount of spin on it. This causes the ball to break down and left diagonally or right diagonally. If thrown correctly, the curveball will look like an arc and it will drop velocity and chances of being hit. A slider is thrown with horizontal spin, causing the ball to break laterally either right to left or left to right. A screwball is thrown with similar spin to a curveball, except it breaks down and right.

Reference:

“Pitch Types | Glossary.” Major League Baseball, m.mlb.com/glossary/pitch-types.

Newton’s First Law of Motion states that every object remains at rest in a straight line unless it change its state because of a external force. Hall of Fame pitcher Nolan Ryan recorded 5,714 strikeouts, using the first law of motion when throwing his fastball. Ryan held his baseball in his glove as he looked at the catcher’s signs. After getting a sign, he went into his windup and throw the ball in motion toward home plate with an overhand delivery.

In addition to Ryan’s ability to throw a fastball at 100 mph, he knew very well the physics of air pressure acting on the surface of a spinning ball. This would be putting lateral spin on his fastball causing the ball to move several inches sideways as it crossed home plate, making it almost impossible to be a hit by a hitter. Very good pitchers use the first law of motion to throw fastballs, sliders and also curve balls.

Newton’s first law is realized at both ends of a pitch. When the pitcher sends the baseball in motion and the hitter sets the bat in motion by swinging. Newton’s Second Law of Motion shows the velocity of a mass object changes when it is projected to an external force. This second law shows the force generated when there is contact is equal to the combined mass and acceleration of both the ball and bat.

Newton’s second law is illustrated when a batter bunts, because the mass of the bat is not in motion. The mass acceleration is provided by the pitched baseball. A very smart bunter uses the mass and acceleration factors at the moment of contact by allowing the barrel of the bat to react slightly to the force generated by the baseball, in other words allowing the bat to hit the baseball without putting any force to the ball. The result is a bunt that rolls to a stop short of an infielder.

Newton’s Third Law of Motion says that for every action there is an equal and/or opposite reaction. Outfielders understand this in terms of a baseball that goes up must come down. Exceptional outfielders have the ability and talent to make calculations as the baseball begins rising when hit. An outfielder might recognize the distance between his location and the projected landing of the ball in order to catch certain balls on the fly.

Reference:

“Newton’s Laws.” Physics of Baseball, forceandmotionbaseball.weebly.com/newtons-laws.html.

An important part of pitching which shouldn’t not be overlooked is the velocity a person can throw ball. Many pitchers goal is to achieve a high velocity, and the fact is that college and Major League Baseball scouts look at a pitcher’s fastball velocity. Coaches as young as the Little League age seem to put a lot of emphasis on fastball velocity and how hard a pitcher can throw, well because at younger age velocity is harder to hit.

The average fastball velocity for pitchers 10 years old and younger is between 40-50 mph. The average change up speed for this age is about 10 mph slower, putting the velocity between 30-40 mph.

Pitchers in the 11 and 12 year old age group are playing in the majors division in Little League. This leagues are where teams are more involved in developing kids rather than playing for fun. The average fastball is between 50-60 mph. However, at this age the players may start to hit puberty, however it is not uncommon to see a pitcher throwing near 70 mph. The changeup velocity at this age is typically between 40-50 mph.

The pitchers in the 13 and 14 year old age group can be heavily involved in travel baseball, finishing up their Little League experience, or tournaments. A typical fastball from this age group is anywhere from 55 mph to 75 mph. A pitcher throwing 75 mph is above average for this age, and their fastball is at a high school caliber. An average changeup for this age is somewhere around the 50-60 mph mark.

A high school pitcher can be anywhere from 14 to 18 years of age. This plays a factor in determining an average fastball velocity, however remember that most high schools have a Freshmen, Sophomore, and Varsity program to break up the large age gap. On the average, a typical Varsity high school fastball is between 75-85 mph, although many good Varsity pitchers will be seeing the upper 80s and low 90 range. The Freshmen pitchers will usually be throwing at a very similar speed to the 13 and 14 year olds, and the Sophomores will be somewhere in the middle. A good changeup for a high school pitcher is a -10 to -15 mph drop from their fastball, so anywhere from 60-75 mph is very common for a high school pitcher.

Once a pitcher its done at high school, they have most likely reached their maximum fastball velocity, however some small gains are still possible, some people work harder than others or they just develop at a older age. The average fastball for these upper level pitchers are 90 mph, but there will always be a rarely group of guys who can throw near to 100 mph. At the lower levels of college baseball, there will still be guys in the low to mid 80s. Changeups for this group should be at about a -15 mph drop from their fastball, bringing the velocity near the upper 70s.

Reference:
Boddy, Kyle. “On Velocity Being the Most Important Thing in Pitching.” Driveline Baseball, Driveline Baseball, 2 Feb. 2018, http://www.drivelinebaseball.com/2013/10/velocity-important-thing/.