Investigating a factor that affects the bounce of a ball.
Aim: To investigate how the temperature of the ball affects its bounce.
Factors, which might affect my investigation, are;
* The height the ball is dropped from
* The surface it is bouncing on
* The type of ball
* The temperature of the ball
* The force applied
* The temperature of the surface
* The state of the ball e.g. wet, old, new, worn
* How the ball is manufactured
* The size and the surface of the ball
* The pressure inside the ball.
Useful ideas, information or equations
From my research into a bouncing ball, I have found that the accepted formula for the relation between the ball’s total energy and the height reached is that there will be the same % drop in both the energy and the height.
For Example:
If the ball looses 10% of its energy, it will loose 10% of its height.
This relationship isn’t directly related to the factor I want to investigate, but every bit of information available can be used. It may back up my findings later on.
Before a squash match, the players hit the ball around the court a few times to get it ‘warmed up’. Nowadays, for professional matches, they place the ball in a special heater, which does this for them. The machine is similar to those used for making toasted cheese sandwiches! This would suggest that the temperature of the ball has something to do with the way it bounces.
Preliminary Work
Aim: to investigate how the temperature of a Squash ball affects its bounce and to devise an accurate method for collecting results.
Method: We set up the equipment as shown on the diagram below. We put the kettle on to boil at different intervals, so that we had different beakers full of water at different temperatures. By having several beakers ‘on the go’ at once, we reduce the length of time it took for our experiment. We put a thermometer into each beaker and watched the readings. We decided not to try and gather any reading from below 0?C or above 100?C. When one of our beakers got to the temperature we wanted we put the squash ball into the water and held it under with a pair of tongs. This ensured that the ball was the same temperature all over. We then dropped the ball, with no added force from a height of 1m. As we were working in a pair, one person dropped the ball and the other watched for its bounce height. In our pair, I measured how high the ball bounced. The first time we dropped the ball was as a rough guide. From this bounce, I got a range of about 10cm in which to focus my attention. Therefore when the ball was dropped again, my eyes were already focussed on the rough area and the results were a lot more accurate. After each bounce of the ball, we put it back into the appropriate beaker so that it remained at the original temperature. This was all done as quickly as possible so that the ball would stay at as near to a constant temperature as we could manage. By recording the results over a five trial period, and taking the average, we allowed for variations in temperature that might have occurred for a particular bounce. We recorded the results as we obtained them. The readings I took were from the bottom of the ball.
Diagram;
Results;
Trials
Temperature (?C)
1
2
3
4
5
6
Average
0
3
6
5
4
7
8
5.5
10
10
12
13
11
11
2
11.5
20
15
10
11
13
17
17
13.5
30
19
20
19
20
18
17
18.3
40
28
30
31
29
25
26
29.8
50
31
29
30
31
29
30
30.0
60
40
43
43
45
43
44
43.0
70
46
47
45
46
48
47
46.5
80
55
53
67
56
55
54
55.0
Conclusion; The higher the temperature, the higher the bounce. As the temperature of the ball increased, the rubber became more pliable and it stretched more when it hit the surface of the desk. Because rubber is an elastic material, it returned to its original shape. This provided a force with which to bounce away from the surface with. As the temperature increased, the rubber was more pliable, had further to travel to get back to its original shape and therefore had more force with which to bounce. This meant that it bounced higher.
I am going to investigate how the temperature of the ball affects how high it bounces.
Prediction; I think that if I increase the temperature of the ball then the bounce will increase also. This is because at hotter temperatures, rubber becomes more pliable and stretches more when it hits the surface. This means that it has further to travel to get back to its original shape and bounces away from the bench with a greater force, meaning that it reaches a greater height.
Plan; I am going to repeat the experiment I did for my preliminary work, but with some alterations.
Things to keep the same;
* I will always use the same ball, squash ball A. This will prevent any variance in the surface or weight of the ball.
* As I am working in a pair with Amy Stringer, I will make sure that we don’t switch jobs. This will eliminate the possibility of us dropping the ball differently or having different reaction times and therefore getting varying degrees of accuracy.
* I will always drop the ball from a height of 1m, with no added pressure, so as to make the test fair.
* Each time I drop the ball it will be on the same surface, the wooden desk because the surface is another factor, which might affect how a ball bounces.
* We decided to increase the number of readings taken at each temperature to ten, this will increase the accuracy of our results. This also means that our average value will be more reliable. We also settled it that we would run a test bounce to define the specific area of the ruler, where we expected the ball to bounce. This considerably helped the accuracy of our results. This is the method that we tried and tested for our preliminary work.
* As in our preliminary work, we used water or ice, in beakers with thermometers to achieve the required temperatures. After suggesting many other methods of doing this, we have decided that this is the best, easiest and most reliable.
* Basically we will set up the equipment as in our preliminary work. We found when doing that experiment, that it was easier to hold the ruler upright with a stand and clamp. We will continue this in our main investigation.
* We will always take measurements from the bottom of the ball.
Things to change;
* So that we get a steady range of results we have decided that a 10? C interval will be appropriate between the different temperatures. This applies for both positive and negative figures.
* As our aim is to only investigate one factor that affects how a ball bounces, the temperature must be the only thing that changes.
Equipment required; beakers, thermometers, meter rule, clamp and stand, squash ball A, the surface of a desk, kettle, tongs, supply of ice.
Diagram;
Method; The majority of our experiment went as described in the plan. We discovered that once you got above 60?C, the ball was too hot to touch. The tongs were required to take the ball out of the water and to drop the ball, but still no force was added as we dropped the ball. We also found out that although water boils at 100? C, by the time you had poured it out of the kettle, taken the temperature and put the ball in, it had dropped to, on average 80? C. We also found that although you could get the ball to a temperature of 0? C with ice, it wouldn’t go below that. We knew that impure water boils at a higher temperature and freezes at a lower one. Therefore we added Sodium Chloride (salt) to our ice to get the readings for -10? C. In the classroom we could not go below this, even with the ‘salty ice’. We solved the problem of the water no longer being hot enough once it was out of the kettle by heating it in a beaker over a Bunsen burner. We also added salt to this to increase the temperature.
Results;
Trials
Temp. ?C
1
2
3
4
5
6
7
8
9
10
Average
-10
1
2
0.5
2.5
1
0.5
1
0.5
1
1.5
1.15
0
2
3
3
3
5
3
5
5
5
6
4
10
10
11
11
12
12
11
11
12
12
11
11.3
20
17
21
21
18
20
19
19
19
20
20
19.4
30
24
24
26
26
26
27
27
28
26
25
25.9
40
38
37
39
37
37
36
35
36
37
35
36.7
50
45
43
44
42
40
39
39
41
42
44
41.9
60
46
50
51
48
49
52
53
46
49
50
49.4
70
56
53
54
53
53
54
54
55
54
53
53.9
80
55
56
57
54
55
55
54
55
57
56
55.4
90
59
55
58
57
57
59
59
58
58
58
57.8
100
67
67
66
68
69
69
68
64
65
60
66.3
Analysis of evidence; Graph 2 shows results for every trial at each temperature. Although the range of results varies, it still shows us a very positive trend. The line of best fit accentuates this. From the graph, you can see that as the temperature increases, so does the height the ball bounced. This reflects my prediction. They appear to be approximately proportional to each other. If this is correct a formula would be;
Temperature ? bounce height.
When you look at graph 1, of the averages from each temperature bracket, the line does not appear to be straight. It looks like it has a slight ‘C’ curve at the bottom and an ‘S’ shaped curve at the top
Conclusion; The higher the temperature of the ball, the higher it bounces. This is reflected in both my prediction earlier and my graphs. When researching a bouncing ball I came across the relationship between the ball’s total energy and the height it reached when bouncing. It said that there would be the same percentage drop in one as in the other. This is another relationship, which relies on two things being proportional to each other. Because of the similarities, I must conclude that there is a very strong likelihood that the relationship I noticed in my graph is reliable. Despite this, it would require further testing before anything could be proven. Using our preliminary work as a guide, we set about planning an experiment, which would provide us with a relationship between the temperature of the ball and its bounce height, The ball bounced higher when it was hotter because the heat made the rubber that the ball is made of more pliable. It therefore compressed more with the force of hitting the hard surface. Because it had compressed more, it had further to travel to return to its original shape (rubber is an elastic material).
Evaluation; in my graph, I had a few anomalous results. This is probably because some of our readings weren’t accurate. If I repeated this experiment, I would concentrate on finding a more accurate way of measuring the bounce. Even though we did a practice run before taking down readings, this obviously wasn’t accurate enough. A better way of heating the ball would have been to heat the air around it and keep it at a constant temperature. This would not have allowed it to cool down, whereas the method we used, despite trying our hardest will probably have allowed the ball temperature to drop. Another thing that must be considered when looking at the accuracy of my results is the way the ball bounced. It did not always bounce straight. When the ball bounced at an angle, the height would have been reduced. We should have taken this into account.
On graph 1, it is the value for 40 ? C which is the most anomalous, but the average of the readings for 90 ? C is also a bit ‘funny’. This compares to graph 2, where the number range for 80? C is the furthest away from the line of best fit. The line also skims just outside the results for 90? C and 40? C. These are both interesting because they are anomalous on both the graphs, but this should, in theory be the case for all the anomalous results because they are based on the same figures. We only had to make a few adjustments to our plan, which are mentioned in the method. When writing the plan, I relied heavily on our preliminary work using it as a guide for the best way to carry out my experiment. If I were to change any part of my method, it would be the way we collected our results because it wasn’t accurate or reliable enough. Another way of measuring the bounce would be to use a Polaroid camera or for even better results, a video camera. If this worked, it would produce images of the peak of the ball’s bounce and we would be able to measure it exactly.
Preliminary work:
Trials
Temperature (?C)
1
2
3
4
5
6
Average
0
3
6
5
4
7
8
5.5
10
10
12
13
11
11
2
11.5
20
15
10
11
13
17
17
13.5
30
19
20
19
20
18
17
18.3
40
28
30
31
29
25
26
29.8
50
31
29
30
31
29
30
30.0
60
40
43
43
45
43
44
43.0
70
46
47
45
46
48
47
46.5
80
55
53
67
56
55
54
55.0
Results:
Trials
Temp. ?C
1
2
3
4
5
6
7
8
9
10
Average
-10
1
2
0.5
2.5
1
0.5
1
0.5
1
1.5
1.15
0
2
3
3
3
5
3
5
5
5
6
4
10
10
11
11
12
12
11
11
12
12
11
11.3
20
17
21
21
18
20
19
19
19
20
20
19.4
30
24
24
26
26
26
27
27
28
26
25
25.9
40
38
37
39
37
37
36
35
36
37
35
36.7
50
45
43
44
42
40
39
39
41
42
44
41.9
60
46
50
51
48
49
52
53
46
49
50
49.4
70
56
53
54
53
53
54
54
55
54
53
53.9
80
55
56
57
54
55
55
54
55
57
56
55.4
90
59
55
58
57
57
59
59
58
58
58
57.8
100
67
67
66
68
69
69
68
64
65
60
66.3
11
1
Physics Coursework – Laura Evans, 10sa
