Fair Testing
The key variable in this experiment is the height measurement from which the ball is dropped. It will be a variable which I will vary and control. To do this I will drop the ball from different heights, e.g. 10cm and then eventually 100cm. In addition, I will use the same ruler, ball and surface throughout the experiment as this will not only make the investigation fairer, but it will in fact increase accuracy. Thereby, fewer anomalies should occur in the results.
Preliminary Experiment
Before carrying out the main experiment I have done a pre-test in order to form my method. This pre-test includes the same variables, factors and equipment that I have mentioned earlier in my method.
Below are the results of my pre test.
I have only used distances of 10cm and 100cm, from which the bouncing ball is dropped. I feel that as these are the both extremes of the range (the lowest and the highest of measurements) in which I intend to use for the main experiment. I am also confident that by using both these heights, it will underline the main pattern in the results that I will obtain from my main experiment.
From doing my preliminary experiment, I have realized that it is quite awkward to measure how high up the ball bounces. So for the experiment it is important that there are a couple of people to contribute to the recording of the results, so that one person can do each job, e.g. I drop the ball and another person record how high it bounces. This is very important as it is easier to get precise results.
This preliminary experiment has allowed me to understand thoroughly in how to carry out the experiment. It has also enabled me to draw up an accurate method for my investigation. In all, the pre test has been very beneficial to my overall coursework.
Physics Experiment
Results
Averages are calculated by totaling the three try’s for each measurement at which the ball is dropped from and then dividing by three.
Analyzing Evidence
From the results that I have obtained it is clear to see that the prediction I had set was correct.
From the recordings in the experiment, it clearly shows that as the height is increased in which the ball is dropped from, the more the decrease in height when it rises back up. To explain this we need to look at the scientific theory of elastic collisions.
As the ball is released from any in particular height, it has potential energy based on its height above the surface. After falling, at the instant before the ball hit’s the surface, all that potential energy has been turned into kinetic energy. As the ball meets the ground, it deforms, and some of the kinetic energy gets stored in the molecules of the ball as they bend, just like in a spring. But some of the energy is lost as heat, as the molecules twist, and some more goes into warming the surface slightly. At maximum deformation, all the energy of the fall has either been stored in the ball or dissipated as heat. Then the ball rebounds upward, releasing the potential energy as kinetic energy. As it does this, more energy is lost to heat as the molecules twist and unbends. The result is that, when the ball starts back upwards, it has less energy than when it began its fall. There is no way to stop this from happening; in any energy transfer, there is always energy
loss due to friction or heat.
When taking this scientific theory into account it is clear to understand, that as the height is increased from which the ball is dropped, the potential energy increases and as a result the kinetic energy also increases.
In addition, according to the law of conservation of momentum the height of the drop must be equal to the height of the bounce; however, the bounce does not reach the initial drop height as some of the energy is wasted. So when the ball hit’s the ground there are many energy factors which occur. For example, the loss of energy in the form of friction between the ball and the surface. Some of the ball’s energy is also lost in the form of sound. Thus providing further evidence as to why the ball’s bounce does not reach its initial height.
Evaluation
I feel the investigation was very successful. The procedures to carry out the experiment were fairly easy and simple as I followed the instructions in my method. The results I obtained from the experiment proved that the prediction I had set was correct.
When analysing, I used scientific knowledge to explain the results that I had gathered. It provided me with enough evidence to suggest that my results had been accurate and concise. The results also supported the decisions of the predictions mainly due to the fact that there were relatively few anomalous points. Therefore suggesting that the results were most likely accurate and that patterns which had been identified, continued for the most part throughout. The few anomalous points which did occur in the graph, are caused, I feel, due to my less than 100% eye accuracy when recording the measurement of the bounce of the ball. For example, when the ball was dropped at 80cm, I might have mistaken the highest point at which it rose, for a lower point.
From analysing my results and taking into account the anomalous points, I estimate the accuracy of the measurement to be within around 5% of their true value.
If I had to make any changes, it would probably involve me changing the way in which I record the results. Instead of having another person drop the ball while I record the rise in bounce, I would swap, as I feel my eye accuracy is not very good, so, I would drop the ball while the other person who should have better eye accuracy, record the measure in bounce of the ball. The equipment however would all remain the same. Hopefully by doing these amendments, the accuracy and reliability of the results would most likely increase.
In my opinion, the experiment was a very fair test as all the equipment remained the same - table tennis ball, ruler, boss head, surface, people involved.
There were no difficulties which I felt I had or incurred during the experiment.
When analysing the results, especially the scientific knowledge part, I could read a lot of extra information available on the internet. This could help me further my knowledge and understanding of the bouncing ball investigation and perhaps enable me to write a better analysis. It could also give me some confirmation about my conclusions as it will have been based and proven on the same investigation before.
In conclusion, I feel that the results I have obtained are fairly reliable and accurate. However, a few changes would probably have made it a lot better.
