Investigating a simple pendulum Essay
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In a way, I think that my experiment was successful. Most people would say that it would not have been a successful experiment if their results did not exactly match some of their predictions, just like my results, but I think that my experiment was a successful one because it made me realise that results will not always match predictions and it is fine to get results different from those you expected because it gives you more things to investigate when doing your evaluation.
I think that my experiment was quite a fair one seeing as each test was done three times and an average result was taken. When I was testing the variables, length, mass and amplitude, I only tested one at a time, keeping the other two variables the same. I performed the experiment in the centre of the work bench, so the pendulum could not hit anyone passing by or and walls or other objects.
As I said earlier in my obtaining evidence part of this coursework I think my results may have been slightly inaccurate seeing as the precision of my results depended on my hand-eye coordination which could not have been the same every time I judged when to stop the stopwatch. I think that my results would be quite easy to reproduce seeing as they all follow the expected patterns and were all taken three times and an average was also taken. I will now be attempting to explain why I think that my results did not match those of the equation:
One of the reasons for this may be that my results could have been slightly inaccurate. Another reason may have been that the apparatus that I used was not as accurate as it could have been. If we look at the table of results for the formula, we can see that as the length increases, the difference between the actual time taken for one swing of the pendulum and the formula result gets closer. This could mean that the formula is meant for slightly larger lengths than 10 and 15 centimetres, maybe something such as one metre and above.
Or it could mean that my results are inaccurate, especially those with shorter lengths, seeing as they swing faster and are obviously harder to get accurate results for. And now I will be attempting to explain why I think that the formula: , did not give a constant result. The reasons are the same as the ones for the above formula, that my results may have been slightly inaccurate and that the apparatus I used may also have been inaccurate. And again, if we look at my table of results, the results of the formula seem to get closer to a constant as the length increases.
This could mean that the formula is meant to be used for slightly larger lengths than those that I investigated or it could mean that my results are slightly inaccurate, again especially with those smaller lengths, seeing as they are harder to time as they swing a lot quicker than the larger lengths. If I had to do the experiment again, I would use some different equipment and I would only investigate length as a variable seeing as I now know that it is the only variable that affects the time taken for one swing of the pendulum.
The piece of equipment that I would want to change most would be the time measuring device that I used. A good time measuring device would ensure both accurate and reliable results, which is what every experiment needs to be truly successful. The best device I can think of would be a light sensitive one which starts a timer when the beam of light is broken, by the string passing through it, and stops it when the beam is broken again.
Using this method would not only ensure accurate and reliable results, but it would allow me to get the time taken for one swing only and not the average of ten swings divided by ten. But such a piece of equipment would be very expensive and would also be very hard to set up, so I therefore think that it would not be possible to use a piece of equipment like the one described above. From looking at my results, I would also change the lengths of the strings that I would time, seeing as when I compared my results to those given by the formulas, the shortest lengths of string gave the most out of place results.
I would probably test lengths of around one metre to one and a half metres. When I got these results I would also compare them to the two formulas I have used throughout this coursework. If I had more time I probably would have done each test five times instead of three to be more sure of reliable and accurate results. I would have also tested a wider range of lengths and then I would have been able to see if my predictions were totally correct or whether they were slightly wrong.
From testing more lengths I would also have been able to find out whether the formula: , worked and also whether the formula: , gave a constant result. And just as a final thought, even though I know it would not be possible, I would like to investigate the effect that gravity would have on the time for one swing of the pendulum. I think that gravity would have an effect on the time taken for one swing of the pendulum seeing as it features in the same equation that helped me to predict that only length would effect the time taken for one swing of a simple pendulum.