cRam Session: The Physics of Baseball

By VCU News staff

cRam Session is a VCU News feature that highlights the breadth of offerings in the VCU Bulletin course catalog and the wide-ranging expertise of the instructors. Associate professor Patrick Woodworth, Ph.D., teaches in the Department of Physics in the College of Humanities and Sciences. He shares quick insight from his course The Physics of Baseball.

Tell us something surprising or truly notable about your course’s subject.

Let me mention two things.

First, most fans know that a curveball breaks as the pitcher throws it toward home plate. From a physics perspective, the ball is basically acting like a tiny airplane wing. Because of the Magnus force, a pitcher can put a lot of topspin on the ball – around 2,500 rpm – and this creates higher pressure above the ball and lower pressure below it. That pressure difference actually pushes the ball downward, so it drops faster than gravity alone would make it.

The second thing is a number that really sticks with students: 400 milliseconds. That is all the time a batter has to (a) track a 95 mph fastball, (b) decide whether to swing and (c) get the bat through the zone. The blink of an eye can take about that long, so if you blink at the wrong time, the ball is already in the catcher’s mitt before your brain even processes the pitch. It really drives home that hitting a baseball is not just hard – it is kind of incredible.

Give us an intriguing connection between past and present on this subject.

In a lot of ways, the history of baseball is the story of how we have gotten better at understanding physics.

For a long time, everything was based on the eye test. Scouts would talk about things like a “live arm” or a “sneaky fastball” without being able to really measure what that meant. Now we have tools like high-speed cameras and Doppler radar systems such as Statcast that can put real numbers to those ideas.

A great example is the rising fastball. Hitters have always said certain fastballs look like they rise as they get to the plate. From a physics standpoint, the ball is always falling, but with enough backspin, it does not drop as much as the hitter expects. What used to be described by feel, we can now explain and measure very precisely.

What is your favorite assignment you have students do?

One of my favorite lessons is on the sweet spot of a bat, because it connects directly to something a lot of people have literally felt.

That sharp sting in your hands when you do not hit the ball cleanly is actually a physics problem. When the ball hits the bat, it creates vibrations. If you hit it near the ends, the bat vibrates a lot, and that energy is lost instead of going into the ball, which is why it feels so bad. But if you hit the ball right at the node, the sweet spot, the bat barely vibrates at all. That means more of the energy goes into the ball.

I like this lesson because students can really feel what is happening. It is a great example of energy conservation, and it shows that the best feeling in baseball, a perfectly hit ball, is really just a very efficient transfer of energy.