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 "How tennis balls are made?" This is for English presentation class. You know, I have so many English classes to take to fulfill the extra degree requirement.

Hello, everyone! My name is Cathy. I have been playing tennis for several years which is what I'd like to do in my leisure time. I have even participated in a tennis team during my undergraduate education. So, let's talk about something related to tennis.

Does anyone have an idea on how tennis balls are made? It's actually a hollow ball. The manufacturing starts with a slug, which is made of rubber and many minerals. The minerals are introduced to change the stiffness and other mechanical properties of the ball. The slug is then reshaped into a half shell by compressing the slug in the mold under high temperature. Two half shells are then brought together and glued against each other to form a sphere. This sphere is called the core of the tennis ball. Finally two tennis felts are applied on the core and stick together with the core to finish the manufacturing.

But, why do we need fuzzes on tennis ball?

First, tennis players gain more control on the direction of the shot through these fuzzes. When the racket hits the ball, these fuzzes offer a friction force in which the spin of the racket can be transmitted to the ball.

Second, compare with the smooth ball, the ball with fuzzes experiences less air drag when flying and results in a longer travel distance. This is also the reason why golf balls have dimples. At the very early age, golf balls are smooth balls. Later, experienced golfers found that used balls with nicks, bumps, and slices in the cover seemed to fly farther. It turns out all these are in close connection with aerodynamics.

"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." And "if you add roughness, 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." (quoted from Mehta)

Isn't it amazing? Big knowledge hides behind a tiny thing. This ends my story about tennis ball. Thank you very much.

Ref. How tennis balls are made?