Task
The way in which a ball bounces depends on a number of factors. Investigate the factors and the relationships between the factors which affect how a ball bounces.
Preliminary Experiment
For the preliminary experiment my partner and I decided to investigate what the suitable ranges would be for dropping a ball from different heights. We decided to use heights to drop the ball between 0.1m and 1.5m, going up by 0.1m each time. This will help us to see what type of results we should be expecting and which heights that I should be dropping the ball from.
We used the same ball each time and also, we measured the height dropped from the bottom of the ball and tried to measure where it bounced back at the bottom of the ball as well. We also repeated each experiment two times for each height so that we could get an accurate result.
The height the ball is dropped from will be the only variable that was a continuous independent variable.
The only dependant variable for this experiment will be the height the ball bounces rebounds back.
We were controlling all of the other variables which include the temperature, surface area, mass, size, hardness, material and pressure on the ball, as well as the room temperature.
Preliminary Results
After conducting my preliminary experiment, I have found out that it is very hard for me to calculate the height the ball bounces back up for heights from 0.1m to 0.4m, so I have decided to not use these measurements for my proper experiment. I have also decided to take five measurements for each height instead of three to ensure that I have as accurate results as I possibly can.
Equipment
- A Ball – mass of 8.095 grams to drop
- Two 1 Metre Rulers – to measure height dropped from and rebound height
- Clamp – to stop metre stick from moving
- Clamp Stand – also to stop metre sticks from moving
- Boss – again ensuring that metre sticks do not move
Diagram
Method
- Set up the equipment as shown in the diagram above
- Begin by placing the ball exactly 2m away from the floor instead of starting from 0.5m as it is easier to work downwards
- Make sure that the bottom of the ball is line with the 2m mark
- Drop the ball
- Watch carefully to see where the ball has rebounded to
- Record the result, remembering to see where the bottom of the ball rebounded back to
- Repeat the experiment at that height a further four times
- Record each of the results and then take an average of your results
- Repeat the experiement again for 1.75m, 1.50m, 1.25m, 1.0m, 0.75m and 0.5m
- Plot a graph of your results, making sure to comment on any patterns that you see
Results
Analysis of Results
By looking at the graphs on the previous pages for the preliminary and proper experiments, it can be seen that the height the ball is dropped from is directly proportional to the height that the ball rebounds back. This backs up what I have said in my prediction and proves that it is correct. I could see that the line of best fit that I had drawn on both of the graphs passed through most of the points on the graphs, and the other points were all close to the line of best fit. There was only one slight anomalous result in the preliminary experiment, when the ball bounced back higher than the point where it was dropped from. This was either because force was applied while dropping the ball or the measurement bouncing back was not measured correctly (dropped from 0.2m, rebounded back 0.21m). This was also another reason why I decided not to use measurements as low as 0.2m in the proper experiment.
The graphs that I have drawn in this experiment are line graphs, for the sole purpose that it is much easier to see if the graph shows a positive, negative or no correlation between the height the ball is dropped from its rebound height. It was not possible for me to use a pie or bar chart because this would not show a correlation as a line graph would.
Conclusions
From my results tables and the graphs that I have drawn, it can be seen that the prediction that I had made was correct and I have carefully followed the original task. I think that the experiment which I conducted was a fair experiment because I took five measurements for each height. Accuracy is still a problem, despite the fact that five measurements are taken because there is only a slight amount of time for you to tell where the ball has bounced back to. Although these inaccuracies are minor, it is always good to have an accurate set of results. The graph passes through the origin and this is why the height the ball is dropped from is directly proportional to the height it rebounds back.
The weight of the ball (8.095 grams/0.0895 N) is known and so is the height (2m). These can be used to calculate the gravitational potential energy of the ball.
Gravitational Potential Energy = Weight X Height
(Joules) (N) (m)
Gravitational Potential Energy = 0.0895 X 2
Gravitational Potential Energy = 0.179 J
Below is a table for the rest of the potential energies: -
Evaluation
I feel that the experiment that I have just conducted went very well because I attained reasonably accurate results and did the experiment with as much care as I possibly could have. The graphs which I had drawn gave almost a straight line as all the points were either close or touching the line of best fit. This is the case for both of my graphs. This experiment was fairly simple and I felt that everything went to plan and that there were no real problems. As I have said before, the only real problem in this experiment was when I was trying to see what the rebound height of the ball was. For this experiment, there were no real safety issues except for the fact that clamps are kept near the edge of tables and you should be careful when moving around to not drop your things on the floor.
This experiment required me to find and record many results, but this was an easy task. The fact that I had recorded so many results made it easier for me to draw an accurate graph from my results. I have taken five measurements for each height and I believe that this was more than enough to conduct a fair and accurate experiment. I would have liked to use some special electronic equipment, such as a laser to see the exact point where the ball bounced back to.
If I was going to expand my investigation, I would definitely investigate the factor of temperature on the ball. I think that this variable will heavily affect the results and I would like to see exactly what happens with these results. The ball would have to be placed in a water bath if the temperature of the ball is to be used, although this variable would be difficult to control. A Bunsen burner could not be used as this is far too dangerous a method of heating. I would also like to investigate the height a different ball, other than the rubber ball which I used, for example a tennis ball. I would like to see that if the height the ball is dropped from increases, the height the ball bounces back up increases at a directly proportional rate, as with the rubber ball which I used. My experiment was done on a marble floor; I would also use other floor surfaces such as glass, wood and even floor covered in carpet. The final thing that I would do to expand my experiment is to drop the ball from a different angle, although this would require applying force to move the ball at a specific angle. It is very difficult to measure the applied force and the angle the ball is thrown at, but this is an interesting experiment to try.
Sources
My Own Knowledge
‘Physics for You’ Textbook
Formulas and explanations from the GCSE Longman Study Guides – Physics
Internet Sites
