"Tennis balls, my liege"

King Henry: "What treasure, uncle?"
Exeter: "Tennis balls, my liege."
William Shakespeare, Henry V, act 1, scene 2

Using that quote as a springboard, I interrupt my considerations of Shakespeare's plays to visit the ever-so-tangentially-related topic of tennis. The other day I recorded myself throwing tennis balls, serving tennis balls, and throwing baseballs at distances of 10, 15, 20, and 25 feet. Knowing the footage was shot at 30 frames per second (I did confirm that by recording a stopwatch) allows me to calculate the speed with reasonable accuracy.

​​The slides below can serve as an example: The ball traveled 20 feet (note the measuring tape) in 5 frames (1/6 of a second), equating to 120 feet per second (20*6), or about 82 mph (120/1.467).

Here is a summary of the results:

• The 23 tennis throws averaged 51 mph, with a low of 45 and a high of 55.
• The 40 tennis serves averaged 77 mph, with a low of 60 and a high of 90.
• The 14 baseball throws averaged 46 mph, with a low of 38 and a high of 54.

And here's the spreadsheet, with all the hard data:

tennis_serves.ods
File Size:	17 kb
File Type:	ods

Download File

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It's astonishing to think professional baseball pitchers can throw twice as fast, or that elite tennis players regularly serve 50% faster - and both with far more accuracy than I'll ever have!

Obviously, this test not flawless - it does not address aim (a tennis serve is worthless if it doesn't land in the service box), and footage with more frames per second would increase the precision of the math - but it gives a pretty good estimate.