If you’ve ever watched tennis, or you’ve ever played it, you may have wondered why is the tennis ball fuzzy? Is it just because of tradition or does the fuzz play some kind of role?
Well, let’s look at the facts.
First of all, it’s tradition: back in the 16th and 17th century when court tennis was first getting started, they would cover cork with cloth, wool and hair. But there’s several performance reasons why you would prefer fuzz on the ball. For instance, top athletes can hit the ball over 150 miles an hour on a service, and on a forehand they might hit it 70 to 80 miles an hour. With that speed, it’s almost at the edge of athletes’ ability to react to it. And so the hair actually can slow down the ball; it increases the drag much in the same way that barnacles on ship will slow the ship down. In the same way, the fuzz will slow down the ball. But there’s more to it. (the article continues after the ad)
Another thing is that fuzz will increase the effective spin. Tennis is a game of putting spin on the ball. That’s due to a force called the Magnus effect.The Magnus effect, or Magnus force was named after German physicist H.G. Magnus. When a tennis ball spins, the fuzz on the ball catches air particles and it creates a boundary layer around the ball. Anytime a ball is rotating in an air stream, it kicks some of the air upward, and there’s a basic law of physics that says if that’s going to happen then the ball’s going to have to move downward to compensate.
Here’s a diagram of how this works:
So a tennis player that puts top spin on the ball, the ball will move down as a result. Or if they put backspin it will tend to float, hang upin the air a little bit longer. No matter the hit, the presence of the fuzz will increase the effect of spin.
So the next time you’re playing tennis and you look at a ball, and wonder why it’s fuzzy, you now know why!
If you like what you read, then you will definitely love this one: This Is Why Golf Balls Have Dimples
Photo: Jean Beaufort / Public Domain Pictures
Sources: Why are Tennis Balls Fuzzy? | The answers to 4 tennis ball questions you never knew you had | Ever wonder why? Here are the answers!