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Technically Tennis

Posted February 15, 2012 2:02 PM by HUSH

While invented in Birmingham, England, in the 19th Century, tennis has become popular worldwide, perhaps only second to soccer/football. The game is fast, easy to grasp, and accessible to spectators, participants and an inexplicable number of young, attractive Russian females (see: Kournikova, Kirilenko, Pivovarova, Sharapova, etc.) The game's worldwide following is evidenced by the locations of its four biggest tournaments (Melbourne, Paris, London, New York) and its induction as an Olympic sport in 1896.

Thank you, Mother Russia. Thank you. ...via All Posters

Tennis also features some of the most notable intersections between sport and physics. Intelligently designed balls, rackets and courts, and precision biomechanics compel tennis' case as more of a physics review course than a sport.

"Pop" Goes the Tennis Ball Can

Tennis balls are packaged in unique, air-tight containers that are subject to two atmospheric pressures. Tennis balls have a high inner pressure (27 psi) to increase their bounce rate; yet regular air pressure on a ball outside of the package is about 14.7 psi. When a ball bounces, air inside the ball is compressed, resulting in the high return force. However, with each bounce some air is lost, along with some energy in the expenditure of sound and heat. The rubber of the ball is exposed to sliding friction, which allows minute amounts of the pressurized air to escape. In professional matches, the life of a tennis ball can be as little as a few serves. To be deemed suitable for competitive play, a tennis ball must have a return bounce of 53%-58%.

...via Hong Kong University

Tennis balls are covered in a layer of durable felt, which decreases the drag on the ball through the Magnus effect. The felt also assists in separating the boundary layer and allows a tennis ball to curve downwards during flight. Veritasium's Youtube channel has a great animation of the Magnus effect and tennis balls. Control on the topspin of the ball is a valuable asset in winning matches.

"Swoosh" Goes the Racket

Watch a pro tennis match and you'll witness pros switch their racket regularly. It may seem obvious, but professionals like to keep their rackets precise. By having very taught string tension across the racket, players are able to better control their top spin, being able to deliver 100 mph+ volleys aimed over their opponent's head, but still landing the ball in the court.

This has a lot to do with a recent technology in tennis racket strings with a long-existent material.

...via The Happiest Mom

YEP. Until 1997, a Belgian company named Luxilon produced elastic strings and straps mainly for women's undergarments. Gustavo Kuerten, 1997 French Open winner began stringing his rackets with their polyester strings for unknown reasons and found good enough tension in the strings to make a permanent change. He'd win two more French Opens and several more championships in following years. Today, rackets are almost exclusively strung by Luxilon polyester strings or competitors' alternates. TAKE THAT CHAUVINISTS!

"UHHHGGG!" Goes the Player

It's that weird moan a player makes when striking the tennis ball: an outburst of energy expenditure that occasionally is the butt of a joke or two. The noise has little to do with the quality of the serve, but may provide a passionate or intimidating edge.

Tennis badboy John McEnroe knows a thing about passionate tennis. (It feels weird to label someone "tennis badboy.")

Of note though is the windup of a tennis player. As the player tosses the ball to themselves, preparing to strike the ball forward, he or she has begun to build kinetic energy to drive the ball. The player plants their rear foot, which begins to explode toward their opponent, along with a hop to gain elevation. The hips rotate along with the torso, and the shoulder completes the kinetic explosion. This is called the kinetic chain principle, as linking mechanics of potential energy overlap to develop a sum of their energy, in this case concluding with a powerful serve.

The location of the serve toss is important as well. With a high serve about a foot in front of the body, a player gains significant angular momentum, ensuring the ball is struck with the maximum amount of kinetic energy available.

"(Insert Onomatopoeic Sound Here?)" go the Courts

The most important factor in determining how the ball bounces on varying court types is the coefficient of friction, which gauges the abrasion between the court and the ball. Official court materials extend to over 160 kinds, but can be generalized to three categories: hard court, grass court and clay court. Grass courts tend to have the lowest frictional coefficient, losing 33% of the ball's velocity speed on contact. This is due to the slick nature of well watered and groomed grass. A clay court will insulate the impact of a tennis ball slightly more and a will reduce the ball speed by about 43%. Finally, hard courts, ordinarily concrete or asphalt, play just slightly slower than grass courts, absorbing about 36% of the tennis ball's energy speed. (s/t welderman)

Yeahhh...not playing tennis here. Nor is my Anna. ...via Archinect

Because the ball is in rotation as it strikes the court, the top half of the ball continues to rotate, while the bottom half of the ball has some of its rotation arrested. A high-friction court means a high bounce, and more time for the player to assess the speed and direction of the ball.


And there it is folks! Tennis: a game invented by nobility to pass time at functions that has been severely altered by bras, dirty courtships and pressure. Wait, I thought Valentine's Day was yesterday.

Resources

Wikipedia - Tennis Ball

Physics Dept., UIUC

Popular Mechanics - Tennis Serve; Tennis Racket

Grantland - The Physics of Grass, Clay, and Cement

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#1

Re: Technically Tennis

02/15/2012 10:08 PM

How come tennis is mentioned in Shakespeare's Henry the Fifth, long before the 19th Century?

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#3
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Re: Technically Tennis

02/16/2012 9:30 AM

Good question Tornado: +1

Tennis, as we know it today, is technically 'lawn tennis', a more popular derivative of 'real tennis'. Real tennis is played with a wooden ball on an asymmetrical court, but fell out of favor in the 1870s.

http://en.wikipedia.org/wiki/Real_tennis

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#2

Re: Technically Tennis

02/16/2012 8:33 AM

In reducing information from his sources, the author appears to have made some errors in reporting the affect of court surfaces on ball performance. He talks about clay reducing ground speed by 43%, grass reducing velocity by 33%, and hard court reducing energy by 36%. I don't think you can fairly compare court performance by using 3 different physical units.

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#4
In reply to #2

Re: Technically Tennis

02/16/2012 9:41 AM

I'd say you're right. A vernacular error I didn't catch, though I'm not sure what 'ground speed' you mean.

Kudos.

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#5
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Re: Technically Tennis

02/16/2012 10:19 AM

GA to you, Hush!

You beat me to it whilst I was having to re register.

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