Ball/Court Interaction (Page 1)

We needed to consider velocity before and after the bounce, the angle the ball struck the court (angle of incidence or angle in) and angle the ball left the court (rebound angle or angle out). As you'll see we also had to break down the ball velocity into the horizontal (how fast it flew down the court) and vertical (how fast the ball popped up) components. We looked at the maximum rebound heights, and the horizontal distance the ball flew to reach that maximum rebound height. We had different types of spin and rates of spin (flat, low topspin, medium topspin, high topspin, medium underspin and high underspin) and four court surfaces (hard, red clay, green clay, and grass).

In the ball spin study from the US Open, we were able to count one variable - the spin - and categorize by stroke or player and present the results. But for the ball/court study some of the factors above were interrelated and dependent on one another. No one average or summary could explain what we observed.

To present the results, Jani decided that we would look at what the experts and/or tennis wisdom tells us about ball/court interaction and compare our results. Professor Howard Brody's book "Tennis Science for Tennis Players" provided a great deal of guidance to us. Howard's book summarizes a lot of the known tennis physics results.

We'll be reviewing court speed a little later in the analysis, but for now let's keep in mind that tennis science and wisdom tell us that for the 4 courts that we conducted experiments on grass courts are considered the "fastest", hard courts are slower than grass, but faster than clay, and clay courts the "slowest".

As you may recall we used the US Open ball on all four court surfaces. In addition, we used a Wilson clay court ball on the green clay, a Roland Garros ball on the red clay (the French Open ball), and a Slazenger (Wimbledon) ball for the grass court.