To investigate how the period of a pendulum depends on its length

Plan

Well pendulums have been around for a long time and have been the centre of timing devices. An example of this are the Grandfather Clocks, their important feature being that they are isochronous.

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One complete oscillation

This basically means that the pendulum takes the same time for every swing. There are many factors that may affect the time for one complete swing of the pendulum; this is called the period of the pendulum. These factors could include the length of the pendulum and the weight of the pendulum. This information will help me decide how many results to take in my experiment. Well in my experiment I am going to measure the time it will take my pendulum to travel different number of distances by increasing the length of the pendulum 5 times. I will repeat my results twice so that they will be fair and accurate. I will keep the weight of the plastersine on the end of my pendulum the same so again the results will be accurate. I will take a range of measurements which will include the 5 different lengths of string that will be 10cm, 20cm, 30cm, 40cm and 50cm. I will then make measurements of the time for 5 swings and then 10 swings. Finally I will find the average for 1 swing from the results I gained from the time for 5 swings, I will do this by dividing by 5. I will do the same for 10 swings and work out the average for 10 swings.

Apparatus

1) Ball of plastersine

2) String

3) Ruler

4) Stand

5) Stop watch

6) Calculator

Method

1) Set up the apparatus carefully.

2) Measure the length of string carefully and keep the ball of plastersine the same length.

3) Then record the time taken for 5 swings and 10 swings using a stopwatch.

4) Take these results for each of the 5 different lengths of string.

5) Repeat the experiment twice.

6) Then record your results in a results table.

Safety

1) Make sure whilst the pendulum is swinging that no one is near it.

2) Clear the worktop before you start the experiment.

3) Keep the stand well away from the edge of the table.

Prediction

I predict that the longer the length of the pendulum the greater time the period.

Results

Length of pendulum (cm2)

Time for 5 swings

Time for 10 swings

Average for 1 swing (5)

Average for 1 swing (10)

10

3.80

8.05

0.76

0.805

20

5.79

10.41

1.158

1.041

30

6.72

12.44

1.344

1.244

40

7.62

15.06

1.524

1.506

50

8.31

16.34

1.662

1.634

1st Results Table:

2nd Results Table

Length of pendulum (cm2)

Time for 5 swings

Time for 10 swings

Average for 1 swing (5)

Average for 1 swing (10)

10

3.49

7.10

0.698

0.71

20

4.53

9.14

0.906

0.914

30

4.92

11.44

0.984

1.144

40

5.01

12.96

1.002

1.296

50

7.50

14.85

1.5

1.485

Analysis

The results tell me that the longer the length of the string the more time it takes for one complete period of the pendulum. The patterns I found in my data were that each time the length of string was increased the time taken for the number of swings was always greater. This was the trend all the way through the investigation. The results support my prediction, which was the longer the length of the pendulum the greater time the period.

Evaluation

On the whole the experiment went well and I ended up with a set of accurate results. The experiment helped me find how the length of the pendulum affects its period which was my main aim. I believe my results are very reliable as they agree with my prediction and I repeated the results once again. I took enough results to support my conclusions and if I was to do the experiment I would probably take even more sets of results as it would make the results even more accurate. I could possibly extend the investigation by using different weights of the plaster cine to see if It affects the period of the pendulum also. Bu overall the investigation was accurate and very interesting.