An investigation to find how temperature affects the bounciness of a squash ball.

Bouncing Squash Ball

The Problem

“It is well known amongst squash players that the ball becomes more bouncy when it has been struck against the wall many times. There are a number of possible reasons for this. It might be that hitting the ball against the wall flexes the rubber and alters it in some way to make it more elastic but the most probable reason is that the violence of the collision heats up the ball and it is the change in temperature, which is the most important factor in determining how bouncy the ball is.

Your task is to investigate how temperature of a squash ball affects its bounciness.”

Aim

We have been asked to investigate what factors could affect the bounciness of the squash ball. This could be due to a number of factors, which are stated below. We will have to design an experiment to test one of these factors (temperature of the squash ball) and see how it affects the bounciness of the squash ball. We will use water baths to heat the squash balls to the desired temperature. We will then drop the squash ball from a fixed height and measure the maximum height at which it reaches when it bounces. We will then have to analyse our results and draw conclusions from them.

The Variables

The independent variables involved in this investigation are those, which could possibly affect the maximum height the squash ball reaches when it bounces. These factors are:

Pressure of air within the squash ball.

If the Pressure of the air within the squash ball was increased the ball would become firmer and therefore more "energetic" in its return to its original round shape. When the squash ball hits the ground it deforms but the pressure within the ball pushes the inside of the ball outwards, which causes the squash ball to bounce back.

Therefore if the pressure within the squash ball was increased the quicker the ball would return to its original shape resulting in a higher bounce. Also the rubber will be easier to bend and therefore less energy is lost through the deformation of the squash ball when it hits the ground.

The temperature of the squash ball.

I expect that if the temperature of the ball is increased the higher the bounce of the ball.

The pressure law states that for a constant volume of gas in a sealed container the temperature of the gas is directly proportional to its pressure.

Therefore this shows, in theory, that if we increase the temperature of the squash ball the pressure within the squash ball should increase. Therefore as explained above, if the pressure is increased the higher the bounce will be of the squash ball.

Also when ...

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The temperature of the squash ball.

I expect that if the temperature of the ball is increased the higher the bounce of the ball.

The pressure law states that for a constant volume of gas in a sealed container the temperature of the gas is directly proportional to its pressure.

Also when the squash ball is warmer the rubber will be easier to bend and therefore less energy is lost through the deformation of the rubber when it hits the ground.

The height at which the squash ball is released from.

When you lift the ball, you give it Potential energy. The amount of potential energy depends partly on the height of the ball. The higher you lift it, the more potential energy the ball has. The equation for potential energy is shown below: -

Potential Energy = Mass x Gravitational Field Strength x Height

The equation above shows that the amount of potential energy the ball has is determined by the height you lift it.

When you drop the ball, the potential energy is changed into Kinetic energy. Therefore the more potential energy the ball has to start with the more kinetic energy the ball will have when it hits the ground and therefore it will bounce to a greater height.

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The independent variable, which I am going to investigate, is the temperature of the squash ball. The dependent variable, which I am going to investigate, is the maximum height the squash ball reaches when it bounces.

When the value of this independent variable is being changed to investigate how it affects how far it travels along the escape road, all the other factors must be controlled in order to make it a fair test

Preliminary work

I have done some preliminary work so that I can plan an appropriate strategy for my experiment. I will be able to use the results and practical ideas to improve my method for the actual experiment and also to improve my predictions.

Here are some measurements from the preliminary work which will help me plan an appropriate strategy:

First I experimented with releasing the squash ball from different heights. The results are shown below.

From these results I can see that the highest bounce occurs when the squash ball is released from the greatest height. When it is released from the maximum of 100cm it only bounces 30cm into the air. Therefore I have decided to release the ball from 100cm ,as when the ball is cooled I expect that the squash ball will not bounce as high. Therefore I want to drop the ball from the highest height possible to ensure that I will get a good measurement if I lower the temperature.

Next I experimented with using different pressures of air within the squash ball. The results are shown below.

Experiment using a Squash Ball with 1 dot.

Experiment using a Squash Ball with 2 dots.

Looking at the results of these experiments I have decided to use a squash ball with 2 dots. This is because this will provide a middle range of results. The results will neither be too small of too high.

Method

Apparatus list:

1 Squash Ball ( 2 dots )

1 Metre Ruler

7 water baths ( 10, 20 , 30 , 40 , 50 , 60 , 70)

1 container filled with water and ice

1 pair of tongs

1 pair of safety goggles

1 clamp

1 retort stand

1 boss

1 peg

First of all, I will gather all the equipment required to do the experiment shown above.

Put on a pair of safety goggles to ensure that no hot water is splashed into the eyes. Now place the retort stand on the desk and attach a metre ruler to one side of the stand using a clamp. (See diagram).

Now pick up the squash ball using the tongs and place it inside the container filled with water and ice for approximately 10 minutes. After 10 minutes take the squash ball out but also read what temperature is on the thermometer within the container as the water may not be exactly 00C. Record the temperature. Now drop the squash ball from the height of 100cm, while your partner looks to see the maximum height it bounces to. Now place a peg on the ruler where the ball bounced to. Then drop the ball again and see if it corresponds to the previous bounce.

This will have to be done very quickly as the temperature of the ball will start to change. Record the results in a neat table.

I will then repeat this whole procedure just described for each of the temperatures shown below. However, the temperatures below are just guides. In the proper experiment it is time consuming and very hard to get these exact temperatures.

I will have to do certain things to control certain variables and keep experimental error to a minimum. These things are shown below:

I will use the same squash ball for the entire experiment. This will ensure that all of the repetitions are the same. If the ball was made from a different material, was slightly larger or if it was a different pressure ( indicated by the number of dots ) it could affect my results and therefore not making it a fair test.

I will use the same metre ruler to measure how far, the ball, bounces in the air.

I will have to start the ball from the same height each time. I will make sure that the bottom of the squash ball is parallel to the 100cm mark on the ruler. (See below).

I will repeat the entire experiment described above, in order to check my results, and to identify and eliminate any anomalous readings.

If appropriate, the average of the two sets of results can be found and this can be used as a more accurate figure.

The Prediction

I think that as the temperature of the squash ball increases, the squash ball will bounce higher. I also believe that the temperature of the squash ball is directly proportional to the height it bounces.

The Scientific Reasoning behind this prediction can be shown below. The source is Encarta 2000 Deluxe.

“Molecules are very, very small, and that there are very large numbers of them at normal temperature and pressure. For example, there are about 27 thousand trillion (2.7 × 1016) in 1 cm3 of air, vastly too small an area, and far too many of them to be seen or felt individually. They are moving at about 500 m/s (1,640 ft/s) and whenever they strike a solid or liquid they bounce off, and continue in a straight line until they hit something else (which can occasionally be another molecule). Each time a molecule rebounds, it exerts a force, and it is the sum of all these minute forces that causes the gas to exert a pressure.

As the temperature increases, the molecules gain kinetic energy and move faster, so each collision on a surface creates a bigger force and, if the gas is in a closed container, the pressure goes up. If the temperature is decreased, however, the molecules lose energy and move more slowly, so that, in theory at least, there must be a temperature at which they would lose all their energy and stop moving, and the temperature could go no lower than this.” This temperature is called absolute zero.

Charles law also states that “The volume of a fixed mass of gas at constant pressure is proportional to its absolute temperature.“

This scientific reasoning from a secondary source shows that as the temperature increases the pressure of a fixed volume of gas increases. Within the squash ball there is a fixed volume of air. When this heats up the molecules will move faster and therefore collide with the inside walls of the squash ball more frequently, hence a larger pressure. If the pressure of the air within the squash ball was increased the ball would become firmer and therefore more "energetic" in its return to its original round shape. When the squash ball hits the ground it deforms but the pressure within the ball pushes the inside of the ball outwards, which causes the squash ball to bounce back. Therefore if the pressure within the squash ball was increased the quicker the ball would return to its original shape resulting in a higher bounce. Also the rubber will be easier to bend and therefore less energy is lost through the deformation of the squash ball when it hits the ground.