# An Investigation into what factors affect the period time of a simple pendulum

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Introduction

Lauren Bennie 10H.3 Physics Investigation

An Investigation into what factors affect the period time of a simple pendulum

Plan

By doing an experiment I will investigate which factors effect the time period of each oscillation on a simple pendulum. This pendulum will consist of a mass hanging on a piece of string.

In my investigation one oscillation consists of the complete to-and-fro motion starting from the centre. (See diagram).

Variables:

- Length of pendulum
- Mass of Bob
- Shape of Bob
- Angle at which the pendulum starts
- Density of Bob
- Gravitational field strength (constant on earth)
- Material pendulum swings in

Dependent Variable:

Time to make one oscillation (period (T))

Preliminary Investigation:

I have decided to investigate 3 different variables;

- Mass of bob

Middle

40

13.5

1.35

50

13.7

1.37

60

13.7

1.37

70

14.2

1.42

80

14.3

1.43

90

14.8

1.48

Analysis of preliminary results:

From these results it is clear to see that the length of the pendulum is the only factor which has a substantial effect on the period of the pendulum. Both the angle of amplitude and the mass of the bob have little effect. Therefore, I will investigate how the length effects the period. There are a few things that I mist change from my preliminary investigation. I used an angle of 30º to drop the pendulum from, I found this too large and feel that it would give better and more accurate results to drop from a smaller angle such as 10º. The increments of the length of the string will be changed to 10cm and the range will be 10cm – 150cm, as this will give a much wider set of results. I will also repeat the results 3 times for accuracy.

Prediction:

I predict that the period will be affected by the length of the pendulum. I predict that an increase in the length of the pendulum will produce an increase in time. I can say this because if the string is longer, it will have to travel a greater distance, so the time period will be longer.

When the pendulum is released its gravitational potential energy is converted into kinetic energy. The pendulum doesn’t lose its energy but just

Conclusion

Evaluate

From looking at my results on the table, graphs and comparing them to the formula I concede that the investigation was successful. I can apply the formula to my results and I got a straight line graph with period² against length and a curved graph for period against length, which from research I can tell is what is expected.

My prediction was correct, as I had predicted the period to increase as the length of the pendulum increased, which happened.

I can see that there were no anomalous results and as I did three sets of results and then found an average they were quite accurate. My results were accurate enough to draw a conclusion.

I found that when taking the results it was not entirely possible to get completely accurate results as there was not an easy way to recognize where to stop the clock, but it depended on your reaction times. I would prefer for there to be some indication of one oscillation if I were to repeat this investigation.

My method gave me evidence that could be said to be reliable as it matches up with information I have found in physic textbooks about the formula and shape of graphs. I feel I had enough evidence as I had 3 sets of results for each measurement to find a average with as well as taking results from a large range (10cm – 150cm). I felt it important to start measuring at 10cm because from 10cm until around 40cm there was a steep increase in time.

This student written piece of work is one of many that can be found in our GCSE Forces and Motion section.

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