These are some of the main variables we will need to take into consideration:
- Mass of the ball
- Size and material of the ball
- Drop height of the ball
- The surface used to drop the ball onto
- Ball pressure
- Conditions and atmosphere
To make it a fair investigation I must only change one variable and keep the rest the same. Some of the variables are simple and easy to keep under control but others could cause problems or are difficult to keep under control. One variable for example, conditions of atmosphere, is very hard to keep under control as it is a natural atmosphere and if you wanted to make it perfect other equipment and scientific knowledge will need to be known. There are still rules you will have to follow though to try and keep the conditions roughly the same throughout the investigation.
Here are each of the variables and how I would control them throughout the investigation:
Safety
Safety is always a matter that must be taken into consideration throughout any investigation as you could be putting your life and others around you, at risk. For this investigation the safety factors are little but still must be noticed. During this experiment no dangerous items, objects, or chemicals are being used therefore it should be easy to stay safe and simple. There maybe the odd factor of staying away from units and corners of tables as you could have a nasty head accident since you could be leaning down to record the results of the bounce height. But I am almost certain that nothing serious can happen unless stupid behaviour occurs.
Items
During this investigation some items will be needed in order to perform the experiment efficiently and easily as possible.
Here is a list of the main items being used throughout the investigation:
- Metre ruler stick
- Ball of some type
- Pencil and paper to record results
Plan cont.
Now with the basic outline of the plan sorted all we have
to is sort out the variable I will change during the
investigation in order to find the best results to conclude my
prediction or theory.
Here is the list of recordings I will use for the investigation:
We felt these would be the right amount of results and would give us a wide range of results good enough to prove and test my prediction or theory and be satisfactory enough for our targets. One more factor we had to consider is how we would make the recordings. Of course all you had to do was drop a ball from a certain height and then see how high it bounces back up again, then work out the energy factors involved, but we were faced with another problem. We had to work out, since it was a rounded tennis ball (a sphere), where we would make the recordings from. We had three options to choose from: the top of the ball, the centre of the ball or the bottom of the ball. After a short discussion we decided to use the bottom of the ball as it would be easier for us to calculate the bounce height and drop height. While doing this a partner would then record the results onto paper while the other performed the experiment.
Last of all we had to decide how many times we were going to repeat the experiment. Since we had a good range of recordings, we decided to repeat the experiment six times at each height and therefore leaving us with a nice set of results along with a good average result. We also felt that it was enough to perform this investigation properly with a good set of results. Since we had already done the experiment three times (preliminary work), we only had another three set of results to do. But little did we know that we were not allowed to include our preliminary work with our results and therefore only had three sets of results.
Results
Key (m) = metres
Exp = Experiment
(cm) = centimetres
(1dp) = 1 decimal place
Engy Conv = Energy Conversion
(%) = Percent
Conclusion
Now from the results you can definitely see many factors that need to be taken into consideration. You can patterns occurring and also see where mistakes were made and need to be fixed.
First of all I am reasonably happy with the results except maybe a few values, but then again nothing is perfect and without mistakes, it makes your evaluation shorter. You can see from the first set of results from the first table that there is a wide range of results, enough to perform this investigation. But then once you work out the energy conversions you can see a pattern occurring throughout the table, except for a few values.
These values are from Experiment 1 – Height 1.6m, Experiment 2 - Height 1.6m and the first few values in Experiment 3. Now these mistakes can easily be made due to they are recorded by the naked eye and therefore and not all perfect by any point. But since there only a few extreme values, you can cancel them out and take the rest of the appropriate data to create many patterns.
For instance in table one you can see from the averages column that the height two of the ball is about twice as great each time you increase the height by 20cm. For example, at 1.0m, the average is 54.3cm, then at 1.2m, the average is 64.3cm; therefore making a 10cm increase in drop height 2 when you increase the height 1 by 20cm. This means that it loses about half its potential energy from its original drop height. About a 50% energy conversion.
In table 2, the energy conversion table, you can also see a regular pattern occurring. But this time it’s not through the averages as much, but per column. You can see that the energy conversion from a certain start point (0.2m) gradually increases to another certain point (around 1.4m) then begins to decrease again. It is a gradual decrease but you can still see that the average energy conversions all stay around 50% which therefore shows you once again, that the potential energy loss is about 50% each time from drop height 1 to drop height 2.
Evaluation
During this investigation I manage to find many errors and corrections in which needed to be fixed and found much room for improvement in which would benefit the experiment if it was to be performed again.
I felt that the experiment did go well in many ways, but then again, improvements can be made from place to place. One thing I would definitely change is the amount of experiments made for the experiment. After I have done my first three experiments I then was told that they are for the preliminary work and therefore couldn’t use them in my official experiment and report. This is a shame, because I would liked to of added them to my report as it would have given me a wider range of results. But due to lack of time I was un-able to do this and therefore time was against me. Nevertheless I carried on with the time I was given and managed to produce three separate experiments and put them into tables.
You can see from the results, that there is the odd value or values out of place, due to the fact that the figure is different to what it should be. This basically means that the naked eye is not always the best option to use for this experiment. To perform this experiment with the utter most perfection, a machine or tool of some type could be used to record the exact height of both height 1 and 2 to perfection. With this you know your results are done properly and no major mistakes were made. Luckily since I had enough results, I could spot where mistakes were made in judging the height 2 of the ball and therefore you can count them as extreme values but mistakes are always going to be made by accident. Therefore there is not much we could have done to have changed this factor.
Another thing I would have liked to have done is to have tried to record the exact mass of the tennis ball, with doing this I can work out Potential and Kinetic Energy at each height and worked out the Potential Energy Loss per result. With this I could have produced more figures in my report which could have supported my prediction with more facts.
