In this investigation I will be investigating the factors that affect a bouncing ball. The part of this wide subject I will be focusing on will be the percentage energy loss.
There are many factors that can be tested in how a ball bounces. All these could be investigated. I will be testing one, and this is the percentage energy loss, but from my results I will be able to compare other things too.
Planning
I will be looking to investigate the percentage energy loss, and this will involve letting a ball fall from a certain height and measure the following peaks of the following bounces. When the ball is dropped from a certain height, depending if the conditions a right, such as type of ball, surface and the starting height, the ball will drop and bounce to a peak lower than the starting height. Then the same will happen from this lower peak, the ball will again fall and will bounce to a lower peak lower than its beginning peak. From this we can already see that there will be a percentage energy loss, from personal experiences with sports and bouncing balls. But we are also aware that from the point of first release, the ball will have potential energy equal to mgh. At the point of release, and on the way down, this potential energy will be turned in to kinetic energy, which is equal to 1/2 mass*velocity^2 .
This will be equal to the potential energy (mgh) at the impact with the surface, but on the way up this kinetic will again be turned in to potential energy (mgh) again at the peak of the bounce. At the peak, of the bounce, all of the kinetic energy will be turned in to potential energy and the velocity of the ball will be 0. For our experiment this will mean that we do not need to depend on measuring each peak that the ball will make, in a short period of time. But at each peak we can stop and start the drop again with out spoiling the results, because we will be giving the ball all of the potential energy that it had before we stopped. It gained it with the height that it reached, and we will be dropping it from that height so the calculation of mgh will be the same.
We also performed a primarily experiment to see weather the tests would work and see if everything would go well. Here are the results.
Hollow ball.
Height in cm
Bounce height in cm
75
48
65
42
55
37
45
32
35
27
25
20
Mighty ball.
Height in cm
Bounce height in cm
75
54
65
42
55
38
45
30
35
24
25
18
Safe test:
It is very important to make sure that the test is as safe as possible. We are not really using equipment that can be dangerous, but things can always go wrong. When you set up the apparatus make sure that the stand and clamp are in good condition so that they will not fall and hurt anyone. When you fasten the clamp make sure you do it with your fingers are out of the way or they will get trapped.
Fair test:
This is an important factor to consider when doing a scientific experiment. For this experiment making it fair is vital because the rebound height is a bit of a problem so we have to make sure that it is as fair and therefore as accurate as possible. I will also have to make sure that the ball is dropped for the height I intend it to be dropped from. I will have to make sure that the ruler is at right angles to the table or the height recorded may be faulty. I will also be keeping the same person doing each reading and action, so that they do it in the same way and the conditions are as close to one as other as possible. The method that I will be using is not very good. There is a big margin for error. Least of all the factor of human error. The equipment that is used is very basic. There are many other pieces of equipment that would improve the accuracy of the test a lot, but we will not be able to use them.
Scientific Knowledge
Prediction:
From the experiment that we are doing, I think that I would except to see the higher you drop the ball from the higher the ball will bounce. Because there is a bigger potential energy and therefore higher kinetic energy, so the ball will move faster and bounce higher. And with each consecutive bounce there will be a greater energy loose because when you allow a ball bounce it does finally stop so the energy must go.
Method:
* Take a stand, a few balls, a ruler and a clamp. Construct the apparatus as seen in the diagram.
* Measure out the drop height that you want to start from.
* Take the ball and measure the mass of it.
* At this height drop it and carefully read off the rebound height. The highest place it bounces up is the rebound height. The ball reaches this height fast and care must be taken when reading the height.
* For each drop perform the test 3 times so that a better degree of accuracy can be taken, and averages can be made.
* Perform the experiment again with different balls if there is time.
Diagram
RESULTS
This table shows the PE and percentage loss for each result taken for each ball.
Ball
Starting PE (J)
Rebound PE (J)
Percentage loss (%)
2nd Rebound PE (J)
Percentage loss (%)
Mighty ball
595
450.5
24.2857
340
24.53
595
450.5
24.2857
374
16.98
595
459
22.857
374
18.52
Ping-Pong
175
120
31.42857
289
+140 (gain)
175
140
20
102.5
26.79
175
120
31.42857
97.5
60.42
Squash ball
164.5
32.9
80
4.7
85.71
164.5
28.2
83.465
7.05
75
164.5
37.6
77.142857
7.05
81.25
Golf ball
325.5
186
42.857
12.55
32.5
325.5
195.3
40
193.5
0.92
325.5
204.6
37.142857
116.25
43.18
Ball
Start height
(cm)
Rebound height (cm)
Second height (cm)
Ball mass
(g)
Mighty Ball
0.7
0.53
0.40
0.85
0.7
0.53
0.44
0.7
0.54
0.44
Ping-Pong
0.7
0.48
0.34
0.25
0.7
0.56
0.41
0.7
0.48
0.39
Squash ball
0.7
0.14
0.02
0.235
0.7
0.12
0.03
0.7
0.16
0.03
Golf ball
0.7
0.40
0.27
0.465
0.7
0.42
0.30
0.7
0.44
0.25
Conclusion:
From the table and the graphs you can see that the ball with the highest rebound height was Mighty ball. This was due to the fact that the ball had the largest mass, and so it would have a higher amount of Potential energy and kinetic energy to rebound with. This ball was very much like a bouncy ball and because it is very dense with bouncy particles we would expect it to bounce a lot.
The Ping-Pong ball was the next most bouncy ball. It has a very hard outer shell that is very dense with quite hard materials. It is filled with are, which makes it very light. These factors together mean that as it hits the surface it bounces up quite high again due to the hard surface hitting the hard table, but the table is not going to move, so the ball bounces up. This is also due to the high pressure of the gas inside making the ball making it hard to squeeze in your hands. When the ball hits the table it is hitting with a very strong structure, so it does not give way and loose a lot of energy, but bounces up strongly. This type of ball is used for table tennis and therefore will need to bounce quite well for a good game of table tennis so that the ball can reach the other player once hit. This means that it is designed in a way so that it will bounce well for a good fast game of table tennis. It still managed to keep quite a lot of energy compared to the golf and the squash ball.
Then, came the golf ball. The golf ball bounced in quite a same way to the Ping-Pong ball. It got quite good bounce because it has a very hard surface with a dense interior. The denseness of this ball acts much in the same way as the air pressure in the Ping-Pong ball, providing a strong structure. But this is much heavier than the Ping-Pong ball, and although weight is seen to be a good thing, this is made up of a quite non-good bouncing material. But a material that can provide a good connection for a golf club, and then bounce a bit on grass, and then roll a long way. This is why it did not perform as well as or better than the Ping-Pong ball.
The squash ball did the worse out of all of the balls. This was because it has a very bad structure. As it impacted with the table the surface area of the impact increased making more energy get loosed, this did not happen with the other balls and that is why they bounced more. The very little amount of energy that was left for the squash ball was converted in to a very little bounce that was very hard to read.
The percentage energy loose bit brought a lot of interesting facts. Which showed a percentage gain for the Ping-Pong ball. This was probably because the person that was meant to let go of the ball probably pushed it down increasing to the energy, meaning that the ball had more than just the potential energy, so it bounced higher. From the results as a whole we can see a percentage energy loss that increases from each bounce, this is because there is less energy to start off with, so the energy left for the next bounce is lower. We can say that the greater the start energy the less energy loss there will be, for the same ball. But the results are not exactly right. This was due to human error, and these results are not being taken in to account. The greater energy loss for each bounce may be due to the time that the ball takes to hit the table and then rise again as it is a short period of time. This could mean that as the ball is rising the weight of the ball has a big affect as there is constantly less and less energy lifting the ball up. Then the amount of energy left to lift the ball up is not enough to do this and to a lower energy to start with this amount of energy left is a big percentage.
Evaluation
As a whole the experiment went quite well. I got sufficient results needed for a good experiment. I took three results for each test, so I could find average for even more accurate result. I think my results are accurate enough for this experiment. This is for many reasons.
The experiment was to get the idea how the percentage loss, and which balls are the most and least bouncy and why. For this we do need an accurate height, that we did not get, because we depended on human error. The speeds of some of the balls was quite fast, and so we were luck in the fact that when the ball reached its peak that the velocity was 0 so this meant that the results were taken easier. We also overcame this problem by having 3 people looking at the peaked heights, and one who was the best taker, which we found from primary experiment had the final say if everyone disagreed. We found that that most of the time we all agreed, or 2 of us did, so I think that the results are quite accurate, because of this and because we performed each test three times so we were able to take a good average. We only kept one variable, which meant that we got a fair test. We did it in the same position, used the same apparatus and same surface, and same people doing the same thing.
The method we used was not the best and certainly not the most accurate way possible with the apparatus that the school has. The experiment was very basic and just satified the needs to get good reliable results. The method could have been improved.
The apparatus we used meant that the test was very quick so we had more time to do more tests and work out averages to make our results better.
To improve the accuracy of the method we could do a lot of changes. First of all the experiment had too much human error involved. When the ball bounced up of the table we had to just guess and say the nearest bounce height of the ball. We could have used a video camera to look at the exact peak for each bounce. Further expeiments could include experiments to see weather changing the contact surface has an impact of the percentage energy loss.
From the graphs there are seen to be no odd results. Energy loss as a pattern went up as the drop height increased. This is what we expected so the results are seen to be quite reliable.
I think I had enough results to draw a conclusion. This was because when doing the experiment I took enough readings, and was able to make averages. Overall the results were good and good conclusions were able to be made so in my mind the investigation was a success.
