Ball/Court Interaction (Page 4)

Let's define the different spin rates in revolutions/second (rev/min). There was quite a variation within each range, but these numbers can be used as a guide.

Below you see a bar chart. There are 7 vertical bars, one for each of the 7 balls we used. The legend (the square box) tells you what each colored bar represents. The label on the x-axis (horizontal) states that this is for the flat (no spin) case. The y-axis (vertical) has the ball angle labeled on it.

We studied the results from 5 different test cases for each ball. Each bar represents the average of those 5 cases. As you can see the average of the US Open ball on the red clay court is 27 degrees.

The angle in was primarily a function of the ball machine. We were able to control the speed and spin rate with the machine to a large extent. Although, the team did their best to keep the settings on the machine as consistent as possible, the ball machine was very sensitive. Even a fraction of a difference in the settings could make a noticeable difference. But in general we see from this bar chart that all the ball angles were consistent (the lowest average is 24 degrees and the highest 28 degrees).