Fuzzy Secrets of the Tennis Ball

Have you wondered why the tennis ball, unlike any other, is covered in felt? Or what players look at before choosing a ball for their service? The answer lies in its aerodynamics.

by Nayan Karnavat

Reading time ~ 3 mins

The early tennis balls used stuffing of various materials like wool and human hair with leather to cover it. In 1870, the vulcanized rubber ball was introduced. To improve its playing properties, flannel was stitched over the rubber. The flannel is now replaced with customized ‘melton’ cloth (felt). But how does it help?

Why is a tennis ball covered with felt.

Felt used over the ball is customized for tennis with more loose strands of fibre than used in clothing. It

Reduces the speed of the ball both off the racket and through the air
Improves ball control by preventing the ball to bounce away wildly after racket impact
Reduces bounce so that the ball bounces at a comfortable height

The felt is often referred to as fuzz, although fuzziness is a state of the felt fibers.

Baggage can slow you down, just like the fur of a Tennis ball. Shed it.

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How topspin and backspin affect ball flight.

3 major forces affect the movement of a ball – gravity and aerodynamic forces of drag and lift. These define the trajectory and speed of the ball.

Gravity always pulls the ball downwards.

Drag: The friction between the ball and the air it is moving through causes drag. Drag always acts in the direction opposite to the motion of the ball tending to slow down its speed as compared to if the air wasn’t there.

Most players are used to objects following the trajectory dictated by gravity and drag. Throwing and catching the ball teaches you to anticipate the gravity and drag acting on it.

Lift: There is another aerodynamic force acting between the felt (fuzz) and the air that depends on the speed, spin imparted to the ball and the fuzz on it. This is called lift (Don’t let the word lift make you believe that it acts upwards – it may act upwards or downwards depending on the spin on the ball).

Topspin: When the ball is imparted a topspin – the top surface is moving against the air flow (high resistance) while the bottom surface is moving with the air. High pressure is created by air near the top surface that tend to push the ball down. This is witnessed as a dip in ball trajectory as compared to its trajectory without any spin. Players use this dip in lobs and passing shots when the opponent is near the net.

Backspin: When the ball is imparted a backspin, the reverse happens – the top surface is moving with the airflow while the bottom surface is moving against it (high resistance). High pressure is created at the bottom that tends to push the ball upwards. That’s why the ball appears to float / hang / glide in the air longer than usual when players slice the ball. The higher the spin the more exaggerated is the effect of lift.

A lot more can be read about this here for the technically inclined.

What do players look at when they choose a ball before service?

A ball with more fluff (threads of the felt opened up due to impact with the racket) will travel slower than others. Worn out ‘bald’ ones tend to travel faster (as long as air pressure inside the ball is same). The professionals will choose less fluffed ones if they want their service to be fast. Alternately they will choose fluffier ones if they want to slow down the pace (when the opponent is consistently hitting powerful returns).

Have any questions regarding tennis? Ask us in the comments below.

Fuzzy Secrets of the Tennis Ball

Why is a tennis ball covered with felt.

Baggage can slow you down, just like the fur of a Tennis ball. Shed it.

How topspin and backspin affect ball flight.

What do players look at when they choose a ball before service?

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Fuzzy Secrets of the Tennis Ball

Why is a tennis ball covered with felt.

Baggage can slow you down, just like the fur of a Tennis ball. Shed it.

How topspin and backspin affect ball flight.

What do players look at when they choose a ball before service?

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Free Social Platform

spyn Social App

Company

Other Products

Misc