Learn how physics make baseball possible with the Durham Bulls

Teachers and the Durham Bulls reveal how Newton's laws of motion play into baseball.

DURHAM — Call me nostalgic, old-fashioned or sentimental, but there are few things that say summer so perfectly as going to a baseball game. 

The balls and strikes, the hotdogs, the cold beverage, the peanuts, the organ playing out those few notes before the crowd yells “charge!”—it’s the baseball we all know. It's the Norman Rockwell painted image of baseball. 

But if you go to a Durham Bulls baseball game on Education Day and meet a group of science teachers, you get a glimpse of baseball from a viewpoint most fans may not think about. 

“I used to think baseball was just about the food and the fans and having a good time,” says Lorraine Rudiak, a fifth grade science teacher at Franklin Academy in Wake Forest. “But a close analysis shows you it's all about science and math.” 

“But a hot dog at a ballpark is still the ultimate, isn’t it?” I ask in reply. 

“Oh no doubt,” says Rudiak. “You can’t just come for the academics, you need the food too!” 

A closer look reveals that physics, the branch of science concerned with the nature and properties of matter and energy, is what makes baseball possible. And while 17th century British physicist Sir Isaac Newton didn’t play baseball, the laws of motion he crafted are in action all over the baseball diamond. And force is the leading all-star player in all three laws of motion. 

Let's take a look, or as the umpire yells, let's “play ball!” 

Newton’s first law of motion states than an object at rest will stay at rest and an object in motion will stay in motion unless acted on by an external force. 

At the most basic level, the baseball would simply stay on the ground forever, until the pitcher applied a force to pick it up. Once the pitcher throws the baseball, it would just keep flying forever until a force acted on it. And those forces could come from a bat when the ball is hit or from a player’s mitt when the ball is caught. Additionally, those forces come from gravity and air friction, which eventually force the ball to the ground. 

“When a ball is thrown, it immediately begins to change speed and direction because of air resistance and gravity,” explains Rudiak. “And that is an example of external forces having an effect on an object in motion.” 

Now let’s go to Newton’s second law of motion, which is written out in an equation: F = M x A. That translates to force equals mass times acceleration.  In other words, the greater the mass of the object being accelerated the higher the force must be.  

Think about the pitcher again, but this time substitute the baseball with a bowling ball. The pitcher can’t throw the bowling ball at a high rate of speed because the mass of the ball is greater than the amount of force the pitcher could apply. 

What about the batter? 

“The faster the ball is coming towards home plate, the more force the batter has to apply to the ball to get it to go further,” says Rudiak, as she watches a Durham Bulls player line a single over the head of the shortstop. The mass of the ball also affects the force needed to hit it a certain distance. "The less the ball weighs, the less force has to be applied, while the bigger the ball and the faster it is going, the more force is needed.” 

Now let’s turn to Newton’s third law of motion. It states that for every action there is an equal and opposite reaction. Or stated another way, when forces collide, every force exerted by the first is met with an equal and opposite reaction by the second force. 

That’s essentially what happens when a batter gets a hit. The action or force of the bat hitting the ball produces the reaction of the ball changing direction and moving away from the force of the bat that acted on it. 

“There are a lot of forces in play when you are talking about getting a hit in baseball,” says Ashton Boger, a fourth grade science teacher at Immaculata Catholic School in Durham. "The ball is applying a force to the bat at the same time the bat is applying force to the ball to get the ball to shoot out. So to get the ball in play, a batter needs to apply a force to the ball that is equal to the amount of force the ball is applying to the bat.” 

The same is true for a player simply holding the ball before throwing it to somebody. 

“Objects push equal on each other, so gravity is acting on the ball, even when the pitcher is holding the ball,” says Vincent Boriak, a fourth grader and student of Mr. Boger's. "So the pitcher has to use an equal amount of force to hold the ball in his hand or the ball would just fall on the ground.” 

Now think about what happens when a pitcher delivers a pitch. The major difference between a fastball, curveball, slider and screwball is the direction in which the ball spins. That’s because the spin causes the ball to disturb the air around it. 

“Anything you throw with over the top spin is going to sink,” says Brent Honeywell. He's the starting pitcher for the Durham Bulls in the game the teachers and students are watching. He shows the students the various ways he holds the ball, depending on what type of pitch he wants to throw. 

“The biggest thing I notice that affects my pitching is the wind,” adds Honeywell. “If the wind is in my face, my stuff is going to be a lot sharper. If it’s behind me, the pitches aren’t going to have as much movement, which makes it easier for a batter to hit them.” 

That makes sense, because the spin forces the air on one side of the ball to move faster than the other, in effect, changing the air pressure surrounding the ball. That’s what makes the ball curve. The wind direction would have an effect on the buildup of air pressure. 

Take a closer look. 

A ball that is spinning forward pushes the air down. That means the velocity of the air relative to the ball’s surface is larger at the bottom of the ball. The higher air pressure at the bottom of the ball pushes the ball up. 

And the effect of the spin is powerful. 

A ball spinning at 1,800 revolutions per minute will turn about 15 times in its journey from the pitcher to home plate. That spin rate adds about one ounce of force on the ball, causing the ball to change its direction by about 1 1/2 feet. 

Science may provide a different way to view America’s favorite pastime. But as Honeywell says looking at the children in the stands, “It’s baseball, and when you see all these kids come out, I remember that’s why I like to play. When I was their age, I wanted to be where I am now. So that is the biggest part of baseball." 

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