Home Run to Sydney Physicist

16 May 2011

While the School of Physics' Professor Rod Cross is well-known for his work with police in helping to solve murder cases, he also studies the physics of sport. Professor Cross has written a book titled, "Physics of Baseball and Softball" that was recently published in the USA by Springer.

The book, aimed at secondary and college physics students, includes topics such as the physics of the collision between a bat and ball, the 'sweet spot' of a bat, mechanics of pitching a ball and swinging a bat, the trampoline effect in hollow bats, measures of bat performance, vibration modes of a bat, ball bounce, scattering processes, aerodynamics of ball trajectories and hysteresis losses.

With the advent of high-speed video cameras, sporting broadcasts on TV are now more technical showing up some of the interesting physics involved in games like baseball.

In fact, every major league baseball venue is now equipped with these cameras. The speed and trajectory of each pitched ball is shown on the TV screen immediately just after the pitch.

Just as in cricket where bowlers can deliver out-swingers and in-swingers and reverse swing balls, pitchers can deliver fast balls, curve balls, cutters, sliders, knuckleballs and a few other odd balls. The amount of swing depends not only on the ball spin and the orientation of the spin axis but also on the orientation of the seam joining the two halves of the leather cover.

The actual trajectory of every ball can be downloaded by anyone interested in analysing the data. Web sites now exist that are devoted to doing just that, where people study effects of wind and altitude and even the aerodynamic influence of stadium design.

Bat performance is regulated by the various governing bodies in an attempt to ensure that no team is advantaged by using bats that perform better than others and to reduce the risk of injury.

The issue is complicated by the fact that the outgoing ball speed depends on the stiffness of both the ball and the bat, on the speed of the incoming ball and the speed of the bat, on the impact point on the bat, on the mass and length of the bat and on the moment of inertia of the bat. For that reason, the regulations governing bat performance keep evolving and are now formulated mainly by interested physicists rather than by amateur officials.

Now, if a player is seriously injured by a ball traveling at 100mph, it takes two teams of lawyers and physicists to sort out the compensation package!

To date no such book has been written (even by North American physicists) where the physics of baseball is described in detail and with relevant equations. This might have help prompt the review in the American Journal of Physics (June 2011), which reads:

Physics of Baseball and Softball, R. Cross, Springer, New York, 2011. This book is destined to be the ultimate reference, supplanting all others, concerning bats, balls, and bat-ball interaction. Americans will be appalled to learn that the author, Rod Cross, is Australian.

That may be a home run to Professor Cross.

Contact: Alison Muir

Phone: 02 9036 5194

Email: 555f101735171e22192a06744714012a3c2b6a561234610e3a