from Amazon
Tuesday, August 30, 2011
Physics of tennis courts
I didn’t know that the surface of tennis matches is not covered by its rule book. Fascinating.
But the physics of tennis — those impersonal forces shaping every shot — are not constant. Instead, they largely depend on three separate factors determined by the court surface.
The most important factor is the “coefficient of friction,” a measurement of the abrasive force between the ground and the tennis ball. Courts with high frictional coefficients interfere with the movement of the ball, disrupting its forward momentum. Think of a sluggish clay court. According to experiments performed by the ITF, a shot hit without spin and traveling at 67 mph will lose about 43 percent of its ground speed after contact with the clay surface, slowing down to a leisurely 38 mph. (The reason clay steals momentum is rooted in the friction of all that loose brick, which clumps around the ball. Each clump is like a little speed bump.) As a result, players have a few extra milliseconds to hit a return....
I remember reading a SI article 25(?) years ago in which a tennis court designer said that he could come up with 5 different surfaces such that each of the top 5 players would be a favorite to win a tournament on one of the surfaces. Probably exaggerated, but of course the winner of the French Open often does poorly at Wimbildon.