Batting Physics

There are two basic laws of physics that determine how hard a ball is hit. One deals with bat speed and the other with the angle of the bat as it strikes the ball. The bat speed is a little hard to follow, but it really makes sense. This example will break the concept down into a few basic pieces and demonstrate why makes sense to use a light bat instead of a heavy one. The distance a ball travels is directly related to the speed at which the balls leave the bat (also the spin as discussed later). All other things being equal, a bat that is swung faster will make a ball go faster than one that is swung slower.

There are two things that are "not always equal" in a fast swing. One is that if the swing is out of control, such as happens when you try to kill the ball, the chance of hitting the ball squarely is diminished. The second is that if a bat snaps back in the players hand when it hits the pitch, the impact of the speed will be reduced Many of the coaches, and indeed many kids, will state that a heavy bat can't be snapped back as easily and therefore more of the bat's power will be delivered to the ball as opposed to lost on impact. For a lousy swing that is true, but if the bat strikes the ball in the power position a light bat won't be snapped back and all of the hitters power will be transferred into the ball.

One way to demonstrate where the power position is to hold the bat directly in front of you and have someone else push it back. You can't keep it in place. Now move to the power position out in front of home plate. Again hold the bat there and have someone try to push it back. This time your partner can't move it.

If the bat can't be snapped back in the power position, then a lighter bat, which can be swung faster, will deliver more speed to the ball as it is hit. Ken Griffey Jr. uses a 31 oz. bat and hits the ball a long ways. It is unlikely that any of our players are 80% as strong as Jr., so using a 25 oz. bat just doesn't make sense. Tony Gwynn uses a 29 oz. bat (until late in the season when he switches to a 28).

The other aspect in hitting the ball for maximum distance is putting the proper spin on the ball. Studies have shown (no, I can't quote which, but check out the internet sites) that the best angle to hit the ball is a downward swing of between 18 & 25 degrees. For line drives, this puts a spin on the ball that makes the ball rise (the same as a rising fastball). It's related to the aerodynamics of creating a low pressure area above the baseball by having the air on top moce more quickly that the air under the ball. The next time you are in an airplane watch during take off as the wings are extended in the front to get more curvature on the surface of the wing. This causes the air on top to pass over the wing more quickly than the air below the wing. This low pressure area actualy lifts the plane off the ground.

For ground balls, this spin makes the ball skip through the field more quickly. The physics involved is beyond this little book, but accept the results. An uppercut swing puts the opposite rotation on the ball that will make the ball drop (like an overhand curve) and take high bounces when it hits the ground.