Investigating how the Length of a Pendulum affects its Period

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Investigating how the Length of a Pendulum affects its Period

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Before this experiment I did some preliminary experiments here I tested whether the angle and height at which a pendulum is dropped from affects its period and whether the weight of the pendulum bob affects its period. I found that in both cases, no matter how big or small, these factors did not affect the pendulums period. My results are at the bottom of the page.

But you can see from my results in the table, that it does not matter what the weight is, or as a matter of fact the angle at which the pendulum starts, the period stays the same.

In my experiment there are variables that I must keep the same. For example there is the weight of the pendulum bob. I have decided to use a medium sized bob, which when was weighed it was 39.9g. Even though my results showed that it did not matter what the weight was I will try to pick and use the same bob through out the experiment. Next I must make sure that I do not push the metal bob when the first period starts as then it would give it extra energy that would not make a fair test. The force of gravity will stay the same on earth whenever I do the experiment and so this does not need to be worried about. Amplitude (or the angle at which the bob is released at) does not matter, as proved earlier. I must also ensure that the corks holding the string are held securely or else the string could slip through and then the length would change.

When I do the experiment I will firstly release the ball and then wait till I am used to the speed of the swing and then start timing. But I shall not just time one period, as this would increase the chance of inaccuracies due to my reaction times. This is because over one period the inaccuracies of my reflexes would be a larger percentage of the overall time. Whilst over 10 periods the inaccuracies would be spread across 10 swings and thus the percentage would be lower. Therefore I shall time the swing of 10 periods meaning that there is less chance of discrepancies. By timing 10 periods rather than 1 the change in time from one length to another will also be clearer. This is because the total time will be larger and thus the difference will be larger between each change in length.  I plan to use a total range across the starting and finishing length along the string of 90 cm. This will be spread across 7 different lengths between the values of 10cm and 100cm. I will time the period 10cm then will make the string 15cm longer before timing the period again. I will repeat the experiment three times for each length; this will give me enough results to create a reliable graph.

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Whilst carrying out this experiment you have to realise some safety issues that are to do with the equipment we are using. The pendulum must be set up away from other people as it could hit them and hurt them. Also secure the stand with some G- clamps to make sure it doesn’t fall on you or anybody else.

My prediction is that as you increase the length of the string the period too will go up. But I do not think this will be a very big change, just large enough for it to be noticed as ...

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This is a good attempt at a report that covers the basics needed: 1. The structure is adequate but could be improved by the addition of more subheadings. 2. The results tables are well presented. 3. Reports should not have a running commentary written into them. 4. The explanation given in the conclusion is well researched. 5. The evaluation contains some good suggestions. 6. The report is missing an introduction, aim and hypothesis. *** (3 stars)