Tennis Ball Fuzz: Why is There Fuzz on a Tennis Ball?

You may have heard this question before, or maybe you just want to know more about what's behind this mystery. So, why is exactly is there that fuzz on a tennis ball?

Interview Question

Believe it or not, the question has been described as one of the top 100 potential questions you may be asked in a job interview. That would be one cruel interviewer, but the question may require you to think on your feet because not many will know the answer, and if you can't do that, you'll be left with a blank face.

The question also requires a strong and fast mind to think about how the fuzz affects what the tennis ball's purpose is and help you at least come up with some kind of reasonable answer so you don't look like a jackass.

Anyway, chances are that you'll probably won't be questioned about this, but it's just good to know that it is potentially an interview question. Now, let's get some real answers.

Why Fuzz?

The fuzz, or felt, on a tennis ball creates more drag through all the fibers, allowing players to have more control over the ball.

The fuzz also helps the tennis ball last longer and resist staining. Looking for a more scientific answer? NASA's got it below!

NASA Wind Tunnel Tests

The good folks at the National Aeronautics and Space Administration (NASA) actually did tunnel test experiments with tennis balls back in 2000.

It's interesting stuff, and you can read all about it here. Basically with the study, wind tunnel tests showed that fuzz affects the flight of a tennis ball far more than previously believed.

There were questions surrounding why the drag force on tennis balls was so much higher than other sports balls. According to Dr. Rabi Mehta, a world authority on the aerodynamics of sports balls, "If you have a smooth ball, such as a ping pong ball, it produces a large air wake, like that of a motor boat. The ball's large wake creates drag that slows the ball's flight."

"If you add roughness, like the dimples on a golf ball, air disturbance near the ball's surface actually helps produce a smaller air wake that creates less air drag, and the ball can go farther."

Mehta said that a dimpled golf ball could go 300 yards, while a smooth one would only manage 100 yards.

"Even though a tennis ball does not have a smooth surface, you get a bigger wake because of the very rough surface, plus the effect of additional drag from each fuzz filament, which I have termed fuzz drag. Fuzz drag makes the aerodynamics of the tennis ball even more interesting since the fuzz elements change orientation with increased velocity and the fuzz wears off during play," he said.

Sources:

http://career-advice.monster.com/job-interview/Interview-Questions/100-Potential-Interview-Questions/article.aspx

http://tennis.about.com/od/tennisballfaq/f/faqballs019.htm

http://www.nasa.gov/centers/ames/news/releases/2000/00_58AR.html