GOLF BALL

Hard wooden round balls were the first golf balls used between the 14th through the 17th centuries.In 1618 the feather golf ball or 'Featherie' was introduced. This was a handcrafted ball made with goose feathers tightly packed into a horse or cow hide sphere. The feathers and leather were fashioned into a ball while wet. As the assembly dried out the leather shrank and the feathers expanded to create a hardened ball. The ball was then finished off by painting it and punched with the ball-makers mark. 

After that 'Guttie' balls were used. The Guttie ball was made from the rubber like sap of the Gutta tree found in the tropics. When heated the rubber could easily be fashioned into a sphere and used as a golf ball.

By the late 1890s, a new type of golf ball had been created, by accident, by a visitor to B.F. Goodrich's rubber goods manufactory. A guy named Coburn Haskell had a golf date with Bertram Work, a Goodrich superintendent, and while Haskell was waiting for his buddy in the factory, he idly wound a bunch of rubber bands into a ball shape—and by bouncing it, discovered it contained a high amount of potential energy. Work and Haskell subsequently skinned the invention with the sap from a Balata tree, and the guttie became obsolete. 

By the 1960s Balata and rubber was done away with and replaced with urethane skins and synthetic resin cores.

The reason why golf balls have dimples is a story of natural selection. Originally, golf balls were smooth; but golfers noticed that older balls that were beat up with nicks, bumps and slices in the cover seemed to fly farther. 

Aerodynamicist looked at this problem and realized that the nicks and cuts were acting as "turbulators", they induce turbulence in the layer of air next to the ball. In some situations, a turbulent boundary layer reduces drag.

A golf ball usually has anywhere from 330 to 500 dimples - depending on which company designs the ball. 

AIRCRAFT TIRES

Aircraft tires are totally different from that of automotive tires.  A tire on a car has it easy compared to one on an aircraft. A car doesn't drive along a sun-baked, 120-degree F taxiway, then climb into sub-zero temps several miles above the Earth, hanging in a 100-mph wind, then come down and smash onto the ground at 80 miles an hour, maybe even bouncing a few times. Not just any tire is up to the mission.

Aircraft Tires fall into two distinct technologies - bias (also known as cross ply) and radial. Bias and radial tires are significantly different to each other and both technologies offer operators features and benefits that might be considered agreeable for particular applications. The aircraft tire is a composite structure of three basic materials:

• Rubber

• Nylon Cord

• Steel

The components are bonded together by vulcanization.

The tread in aircraft tires tends to be straight line while your car tires have much different tread patterns. Aircraft tires are filled up to nearly 200 PSI whereas car tire typically are filled up to 30 PSI.

Automotive tires are inflated with normal air. The tires of airplanes (at least the big ones) are inflated by nitrogen (instead of air). Air has a certain moisture content and it is generally very hard to remove this moisture. If an airplane tires were filled with air, at the flight altitude ice would form inside the tires since the temp up there is about -30 degrees F. Landing with a chunk of ice in the tire would make it out of balance and change the tire pressure. Tires would probably burst. On the other hand, nitrogen doesn't form a liquid till -173 C and pure nitrogen has almost no moisture. 

They are also subjected to tremendous forces on landing when they must accelerate very quickly. The friction on touch-down creates great heat within the tires and produces very high stresses in the walls of the carcass. Therefore, every effort is made to reduce or eliminate the deterioration caused over time by oxidation. Since normal atmospheric air is approximately 20% oxygen, the tires are inflated with 100% nitrogen - a relatively inert gas.  Jet airline tires are fused. When the fuse is heated it deflates the tire so they don't explode.

Aircraft tires do not typically have a definitive lifespan. It all depends on the airframe and how hard the landing is. Another factor that many people overlook is the main vs nosewheel tires. The main tires tend to last longer than the nosewheel tires. Depending on the aircraft this could vary from 10-200 landings. Once a tire is used up it isn't thrown away, it's retreaded up until the core becomes worn out.

TENNIS BALL

History

The very first tennis balls date back as early as the 15th century and were made of different materials, mostly from leather stuffed with human and horse hair or wool. The Scottish craftsmen used the stomach of a sheep or goat that they wrapped with wool and tied with a rope. In the 18th century, strips of wool were tightly wound round a nucleus made of cork. Tennis balls with a cork core and cloth covering are still used in the original game of tennis, known as Real Tennis.

Modern composition

In 1870, vulcanized rubber was first used to manufacture tennis balls. The Germans were well known for developing vulcanized air filled rubber balls. Constant improvements were being made to the ball, by wrapping flannel around their surfaces and later using a felt on the exterior. Pressurized tennis balls started to be manufactured, and are being used today.

Around 300 million tennis balls are produced each year. The most expensive material when manufacturing a tennis ball is the felt covering the ball. There are more than 200 tennis ball brands that have been approved by the ITF. Standardization approved by International Tennis Federation :-
- Size – the diameter of a tennis balls is 6.35-6.86 cm (2.50-2.70 inches)

- Weight – must be between 56.0 g – 59.4 g (1.975 -2.095 ounces)
- Rebound Height – between 135-147 cm (53-58 inches)
- ATP and WTA tournaments are played with yellow tennis balls, that were introduced in 1972 following research that demonstrated their easy visibily on colour television. White balls were used prior to this.

All tennis balls are tested in the following environment:
- Tempereature 20°C / 68°F
- Humidity 60%
- Atmospheric pressure 102 kPA

Production

Tennis ball manufacturers mold rubber into two shapes that are pressed together to form the core of a ball. To achieve an appropriate level of bounciness, tennis ball makers inject a specific amount of pressurized air into the center of each rubber core. Manufacturers buff the sealed, pressurized rubber balls and cover them in glue. Machines cut long pieces of bright yellow felt into two shapes that are wrapped around each tennis ball to form a covering. Ball makers heat the completed tennis balls to make the glue form a seal that holds the two pieces of fabric together.

Why tennis ball bounces?

The anatomy of a tennis ball features a hollow rubber-like core filled with gas. The molecules that make up gas are relatively unorganized; they readily slide around and over one another to fill up any space they occupy. As such, gas molecules can easily expand or contract. When a tennis ball hits the ground, the force presses up against the ball, pushing the bottom surface of the ball in and compressing the gas inside its core. As the tennis ball returns to its normal shape, the gas inside the ball acts as a spring and causes the ball to bounce into the air.

Amazing uses

• Keep a swimming pool oil-free - Float a couple of tennis ball sin your swimming pool to absorb body oil from swimmers. Replace the balls every couple of weeks during period of high use.
• Fluff down-filled clothes - Down filled items like jackets, vests, quilts, and pillows get flat and soggy when you wash them. You can fluff them again by tossing a couple of tennis balls into the dryer when you put them in.
• Make a bike kickstand for soft soil - to prevent a bicycle kickstand from sinking into soft grass, sand or mud, cut a slit in a tennis ball and put it on the end of the kickstand.
• Tennis balls are actually pretty difficult to recycle and most go to their 2^nd life as anti-scuff devices on the bottom of chair legs.  However, the balls from Wimbledon are used as homes for the endangered Eurasian harvest mouse.  Other uses include covering it in vasoline and hanging it outside to deter bugs, cutting them open and hiding things in them.