The Physics of Baseball

     Spring means many things to people, lengthening days, first flowers, warmer weather and for many, spring training of their favorite baseball team. Baseball and science have had a place in my life for a very long time and so it is little wonder that I've managed to combine the two topics. 
Baseball is more than just a sport, it's  cool demonstrations of basic physics!

     Every major league team strives to have talented pitchers on their team. There are many types of pitches, fastballs, sinkers, sliders, and curve balls are a few. Curve balls have always fascinated me because a really good one is an art. But what makes a curve ball curve?

     A curve ball curves because the pitcher throws the ball in such a way that the ball spins. As the ball spins, it creates a drag. There is air flow on both sides of the ball. But on one side of the ball, the air flow is the same direction as the air which is rushing past the ball. This has the effect of speeding up the air flow. On the other side, the air flow is reversed and is opposite the air rushing past the ball. This slows down the overall air flow on that side of the ball.  The grater the velocity of the air, the less pressure it exerts. This means that the ball has more pressure on the side with the slower air flow. The uneven pressure causes the ball to move to one side, or to curve.

     Since the goal of baseball is to score more than your opposing team, it pays to know what increases the chances of hitting a homerun. Which goes further, when hit, an average speed pitch or a fastball? Most people who are asked this question think that a hit ball will go farther if it was pitched slower but that is not correct.

     A typical baseball bat is about five times heavier than a regulation baseball. If the batter swings the bat with a speed close to the speed of the pitch, the bat will have about five times more momentum than the ball at the time of collision and most of the collision energy will be transferred to the ball and the momentum of the bat will barely be affected. If you find this a bit hard to grasp think of a comparable example: look at the difference between gently tossing a ball at a wall and throwing the ball with force. The harder you throw the ball at the wall, the farther it will go on rebound. Faster pitches will result in longer hit balls.

     Regardless of whether the ball sinks, slides or curves, the batter would like it to be low and inside. Most batters call this the "home run pitch."  Is there something better to low and inside? Or is this just one of the many superstitions connected with the sport?  A "longball" is a combination of swing timing, collision location on the bat, and pitch location. There are two main advantages to hitting a low inside pitch.

     First, in a low, inside pitch the spin on the ball will be closer to true backspin  and will generate some lift to the ball. This will increase distance. Secondly, the bat can be swung faster closer to the body. When a batter swings a level bat gravity is pulling perpendicular to the plane of the swing requiring some amount of effort on the batters part to counter-act it. On a low inside swing, the force of gravity is much more parallel to the plane of the swing.

We could of course, produce nice mathematical calculations to prove all this stuff. But somehow, it's more fun to just watch the game and call it a visual lesson in physics!