Title: Temperature Equilibrium in Squash Balls.

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A2 Physics Coursework

Title:         Temperature Equilibrium in Squash Balls

Aims:

  • I aim to investigate aspects of temperature change in squash balls. For a squash ball to be used in a match it should be warmed up first; I wish to investigate how many strikes of the ball a player must have to warm the ball up.

  • I also aim to find the optimum temperature of squash balls, when the heat loss to surroundings will be equal to the heat gained from the deformation process.


I am a keen sports player, and have been very interested by how differing balls can affect sport, for example, during this summer’s ‘World Cup 2002’ in South Korea, the balls used were said to swerve more, and would cause more problems for the goalkeepers.

I also have first hand experience of seeing how different cricket balls can affect games, as all balls are produced with slightly different characteristics. Some balls behave differently depending on different weather and pitch conditions.

It was this that made me more interested into how various types of squash ball were different. I did not originally understand how the different colours of the balls affected how the balls reacted in terms of the bounce: whether it depended on the temperature of the balls and/or their elasticity.

I started by dropping a squash ball onto a perfectly hard floor. It will rebound, but even the "liveliest " ball will not rise back to its starting position. Why does it bounce back, and why does it loose height on the rebound? What are the forces involved? Why do players warm up the ball before starting a match?

Sources

Initially I used an Internet search engine () to look for information on squash balls.

The sites I found most useful were:

 (website of the sports governing body)

 (manufacturers of 90% of balls)

 (University of Virginia)

I also read an article called “Bounce, Balls, and Surface Temperature: A look at seven different squash balls and how surface temperature affects their bounce” by Steve Edgar, an American researcher and squash fanatic, in January 2000.

I obtained a copy of the Rules of Squash publisher by the World Squash Federation (”WSF”) as I had discovered there were strict guidelines on the manufacture of both squash balls and the courts.

Finally I e-mailed Paul Walters of Dunlop Slazenger International to see if the company could provide me with graphical or statistical data relevant to my coursework.

My research showed that Dunlop are the manufacturers of over 90% of the world’s squash balls, and therefore it makes sense to conduct my experiment with Dunlop’s balls, as they are the most commonly used for the average player, as well as the type professionals use in tournaments.

There are four grades of balls commonly differentiated by a coloured spot or dot on the surface of the ball.

The blue dot ball I used, a Dunlop Max, was developed to ensure that players enjoy their initial introduction to the game and are able to quickly and easily develop correct technique and therefore improve their skill level. The Max ball is 12% larger than the standard size with a 40% longer hang-time compared to the yellow dot ball (Revelation Pro). It supposedly doesn’t need to be warmed-up and is fundamentally different from the yellow, green and red balls I used.

Rationale 

The WSF specifications for the yellow dot ball used in tournament play (see Appendix 2) are particularly concerned with the Rebound Resilience of the ball – this is the degree to which the ball bounces to its former height when dropped on the court floor from a height of 254cm.

There are no specifications for the other coloured balls, however the guidelines state that the rebound resilience at 45oC for blue balls (as used by beginners) is 36-38% and for red balls (intermediate) is 33-36%.

The balls are made from slightly different polymer compounds to produce these resilience properties.

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Elasticity of balls

On impact with a racket or the wall, a ball flattens or compresses, regaining its original shape as it pushes against the surface and rebounds. The property of a ball that causes it to regain its original shape is called its elasticity.

Energy changes on impact

A moving ball has kinetic energy (energy of motion). On impact, some of the kinetic energy is stored in the ball as elastic potential energy. As the ball returns to its original shape and starts to rebound, the elastic potential energy is converted back into kinetic energy. Some ...

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