Pressure of air in ball- This factor will depend on the factory pressure of the ball and the temperature of the ball. The higher the pressure, the higher the ball will bounce. It is difficult to control this factor.
Gravity- A larger gravitational force would cause the ball to fall faster and give more resistance to the ball bouncing up. This factor is nearly impossible to change.
I have decided to experiment with TWO factors: heat and height. These were the two easiest to control and gave good ranges to work within, therefore the two that will give the most accurate results. I will keep all the above factors constant except the factor I am investigating and investigate my two factors SEPERATELY, keeping one constant whilst testing the other. Otherwise it would be impossible to tell which factor was effecting the bounce.
I will use a Ping-Pong ball for testing the factor of height, and use a golf ball and a squash ball for the temperature factor, doing two sets of the experiment (one with each ball) and comparing the two. I will NOT use results from one ball into another’s results table/graph. This would be unfair because the balls differ.
Prediction
I believe that when the ball is released form a higher point, it will bounce to a higher point. I also believe the two events will be proportional: If you bounce the ball from twice as high, it will bounce twice as high This is because energy cannot be created or destroyed so if you double the height, you double the potential, you double the kinetic energy and therefore double the height. I believe the graph will go through the origin because if there is not height there is no energy for the ball to bounce with.
I predict that for my temperature experiments, the ball will bounce higher as the temperature gets warmer. This is because as it gets warmer the atoms in the ball vibrate more. This means that when it hits the ground the atoms push the outer wall of the ball, keeping it more rigid and forcing the ball to bounce higher. When the temperature is lowered the opposite occurs because the atoms have less energy and hit the wall of the ball at a slower speed and at a slower rate. I believe this graph will NOT go through the origin because if the temperature was at 0°C, the ball would still bounce to an extent because it has kinetic energy from the height it was bounced from.
Method
Apparatus (both experiments)
Water bath, thermometer (measuring to nearest degree Celsius and with a range of 0°C to 80°C), water, kettle, 1 Ping-Pong ball, 1 golf ball, 1 squash ball, 2 metre rulers (with ranges of 0cm to 100cm at 1cm intervals), clamp stand, table.
Temperature: We will set up the apparatus as shown in diagram (overleaf) and then heat the ball to a set temperature (measuring temperature using a thermometer to the nearest °C.) We used a water bath and subsequently (for high temperatures exceeding 40°) water from a kettle to heat the ball. This is to minimise danger of burns e.g. from a Bunsen Burner
Quickly, so as to keep the temperature constant, we will then drop the top of the ball from 100 cm high (measuring with the metre ruler) and measure the bounce to the nearest cm of the TOP of the ball. We will always measure the top of the ball to maintain consistency. We will repeat the measured temperature another 4 times to gain an average, reheating the ball if required. This is because a bouncing ball is hard to measure very accurately, so a set of 5 repeats is needed for reliable results. We will then repeat the cycle of five results for the next measured temperature. To keep the experiment fair the only thing that we will change each time when investigating this factor will be the temperature. We will use the same ball throughout the experiment and check the ball was at the same temperature each time. We will drop it onto the same table from the same height. The range of temperature we will use are from 20°C to 80°C and taking readings every 10°C. We will accurately record the results. Once we have tested the squash ball for whether temperature effects the height of the bounce, we will repeat the entire temperature experiment with the golf ball, keeping the same method. Only general common sense is needed to prevent injury.
Height:
We will set up the apparatus as shown in diagram (overleaf) then drop the top of the ball from 30cm high (measuring with the metre ruler) and measure the bounce to the nearest cm of the TOP of the ball. We will always measure the top of the ball to maintain consistency. We will repeat the measured height another 5 times to gain an average, reheating the ball if required. This is because a bouncing ball is hard to measure very accurately, so a set of 5 repeats is needed for reliable results. To keep the experiment fair the only thing which we will change each time when investigating this factor will be the height. We will use the same ball throughout the experiment, therefore cutting out any factor variables. We will drop it onto the same table. The range of heights we will use are from 30cm to 150cm. We will accurately record the results. No safety precautions are needed for this experiment.
