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Additional Science - What affects the period of a pendulum?

Extracts from this document...

Introduction

ADDITIONAL SCIENCE COURSEWORK – Investigating factors that affect the period of a pendulum.

There are several factors that could affect the period of a pendulum. Factors such as the length of the string, the height from where the ball bearing is dropped from, the material of the ball bearing and the weight of it can affect the period. I can control the length of the string by having several different lengths of string (measured accurately), and change the material of the ball bearing and the size of it.

By doing the preliminary experiments I can see which factor affects the period of the pendulum the most and then have that as my main experiment to elaborate on it. Once that is completed, the results will be recorded and presented in a graph. A conclusion on the results and an evaluation will also be included.

To make the preliminaries and the main experiment a fair test, I will:

  • Have to make sure that the string used to tie the ball to the apparatus will be the same material throughout the preliminaries and main experiment.
  • Keep the size and the material of the ball the same, unless for the experiment where I have to change the ball bearing, because each ball varies in weight so by changing it midway of the experiment would affect the outcomes.
  • Have the same person keeping record of the time taken with the stopwatch, because by changing the person in charge of the stopwatch could result in time differences, as everyone has different reaction times.
  • Use the same ruler throughout the experiments as another ruler could be different by a few millimetres.
  • Drop the ball bearing from the same height and angle, unless for the experiment where I am testing to see how a change in angle and height affects the period.

EQUIPMENT: image00.png

  • 1 retort stand                
  • Ball of string                  image01.png
  • Metal ball bearings
  • Protractor
  • Stop watch
  • Electronic scaled
  • Scissors
  • 30cm ruler
  • Elastic bands
  • Cello tape
...read more.

Middle

1.16 secs

1.15 secs

1.16 secs

1.10 secs

1.13 secs

STEEL

18.98g

1.16 secs

1.03 secs

1.09 secs

1.00 secs

1.03 secs

1.10 secs

1.07 secs

IRON

40.85g

1.09 secs

1.04 secs

1.12 secs

1.03 secs

1.10 secs

1.09 secs

1.07 secs

Looking at the results for this preliminary, I do not think these results are reliable.  I assumed that the results would show that the heavier the ball bearing, the less time I would take to complete one oscillation. However it seems that the results are almost similar, and it also includes 2 outliers. A possible cause of the similar results may be due to human error, as an error could have been made when timing and the reaction of both the time keeper and the person dropping the ball bearing. Furthermore, an error could have been made when weighing the ball bearings, as the scales were slightly faulty this would have affected the accuracy of the weighing.

Preliminary Test #3:

In this preliminary I am testing to see how changing the angle for dropping the ball bearing will affect the time taken for the ball bearing to complete one oscillation. The independent variable in this test is the angle and the control variables are the length of the string, the material of the ball bearing and the stopwatch keeper.

METHOD:

  1. Choose a ball bearing of any material.
  2. Measure 30cm of string, not forgetting to leave a bit extra to make a loop for the ball bearing then attach it to the retort.
  3. Get the protractor and attach it to the retort with cello tape, so it makes it easier as well as improving accuracy.
  4. Get a partner to help you drop the ball bearing.
  5. Check that you start the stopwatch as soon as your partner drops the ball bearing.
  6. Stop the stopwatch as soon as the ball bearing makes one oscillation.
  7. Once all the angle changes have been tested, repeat the test again to make the results more reliable.

ANGLE:

STRING LENGTH:

TIME #1:

TIME #2:

TIME #3:

TIME #4:

TIME #5:

TIME #6:

AVERAGE:

180°

30cm

1.31 secs

1.19 secs

1.19 secs

1.13 secs

1.10 secs

1.19 secs

1.19 secs

160°

30cm

1.18 secs

1.00 secs

0.93 secs

1.18 secs

1.13 secs

1.06 secs

1.08 secs

140°

30cm

1.06 secs

0.93 secs

1.00 secs

0.99 secs

0.93 secs

0.81 secs

0.95 secs

120°

30cm

0.65 secs

0.87 secs

0.81 secs

0.90 secs

0.94 secs

0.84 secs

0.84 secs

100°

30cm

0.69 secs

0.69 secs

0.81 secs

0.54 secs

0.75 secs

0.63 secs

0.69 secs

ANGLE:

SPEARMAN’S RANK:

AVERAGE:

SPEARMAN’S RANK:

d^2:

180°

5

1.19 secs

5

0

160°

4

1.08 secs

4

0

140°

3

0.95 secs

3

0

120°

2

0.84 secs

2

0

100°

1

0.69 secs

1

0

...read more.

Conclusion

IMPROVEMENTS:

The main concern regarding improvements is the equipment again. The stopwatch is one of the pieces of equipment that could be improved.  A quicker responding timing device would have increased the accuracy of the experiment, as sometimes the start button would jam, therefore delaying the time and affecting the test.

Furthermore, the measuring of the lengths of string could also be improved. By using a ruler marked with millimetres as well as centimetres would improve the accuracy of the experiment as it would enable us to cut the string to the perfect length.

Even with such small improvements to the method and the equipment, I think it would make the results even more accurate, and possibly to get results with no outliers included.

CONCLUSION:

To conclude what I have discovered in carrying out this experiment, I found that my hypothesis was proved and that length of the string affected the ball bearing a lot, but it would also be even better if the results were even more accurate and if there was no outliers at all. I also realised that not only did the length of the string affect the period of the ball bearing, but other factors such as the equipment also affected the results.

If it were possible, I think I would do one more experiment, changing another factor to see which variable affected the time the most, that way a more solid conclusion could be drawn.

...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a good report that covers the basics of this investigation.
1. The start of this report should have an introduction.
2. The results tables are well presented.
3. The conclusion is very short and should include data.
4. The evaluation focuses on this investigation well but should include some suggestions for improvements.
*** (3stars)

Marked by teacher Luke Smithen 05/07/2013

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