# An Investigation to See Which Factors Affect the Swinging Of a Pendulum

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Introduction

An Investigation to See Which Factors Affect the Swinging Of a Pendulum

Aim

Our aim is to find out whether changing the variables of the swinging pendulum affects the speed.

Preliminary Work

In order to find out which variable/s affect the swinging of a pendulum, I need to test all the variables available.

There are three variables we will be investigating:

- The length of the string
- The mass of the pendulum
- The angle from which the pendulum is swung

For each experiment, I will change the length/mass/angle five times, and repeat each length/mass/angle just once. Therefore, I will be doing a total of 15 experiments.

Experiment 1

I will investigate the relationship between the length of the string, and the time it takes for the pendulum to make 1 full swing.

- Hypothesis: As the length of the string increases, so does the time.
- Procedure: We will test how long it takes for a 80g weight attached to a string to swing from one point and back to the same point. We will use various lengths of string to test the times of the swing.

However, I will measure the time taken for 10 oscillations rather that 1 and then divide the result by 10, in order to eliminate as much time and reaction error as possible.

Exp 1

Changing Length (variable)

Mass = 80g

Angle = 5o

Length (in metres) | Time (in seconds) (for 10 swings) | Time (in seconds) (for 1 swing) |

L1 - 0.5 | = 16.46 secs | 1.65 |

L2 - 0.4 | = 13.98 secs | 1.40 |

L3 - 0.3 | = 12.42 | 1.24 |

L4 - 0.2 | = 10.91 | 1.09 |

L5 - 0.1 | = 8.71 | 0.87 |

These results show me that the length of the string does affect the time for the pendulum to swing.

Experiment 2

I will investigate the relationship between the weight of the pendulum, and the time it takes for the pendulum to make 1 full swing.

- Hypothesis: I don’t think the weight will affect the time.
- Procedure: We will attach a string to a stand. At the end of the string, we will attach a weight. We will then release the string and the weight, and we will let it swing through the air. We will time how long it takes for the weight to travel through the air and return to the starting point. After we record the data, we will replace the original weight with one of a different mass. We will repeat this process five times.

Exp 2

Changing Mass (variable)

Angle = 5 o

Length = 0.3 (30cm)

mass (in grams- g) | Time (in seconds) (for 10 swings) | Time (in seconds) (for 1 swing) |

M1 - 100 | = 12.45 | 1.25 |

M2 – 80 | =12.43 | 1.24 |

M3 – 60 | =12.54 | 1.25 |

M4 – 40 | =12.32 | 1.23 |

M5 – 20 | =12.26 | 1.23 |

Middle

(for 1 swing)

A1 - 10

= 12.14

1.21

A2 - 20

=12.27

1.23

A3 - 30

=12.42

1.24

A4 - 40

=12.56

1.26

A5 - 50

=12.79

1.28

These results show me that the angle of the arc does not affect the time for the pendulum to swing.

What My Preliminary Work has Shown Me

My preliminary work has now shown me that the only affecting factor in this investigation in the length of the string. Therefore, this variable will be the only one I will be using in my final investigation. After completing three experiments, I concluded that the only factor affecting the time of the swing of a pendulum was the length of the string. The hypothesis for Experiment 1 was correct, as was the hypothesis for both experiments 2 and 3, the weight on the string, and the angle of the arc. The time increased as the length of the string increased. The following graph shows how the length of the string (the independent variable) affects the time (the dependent variable).

Diagram

Key Factors Identified

Apparatus:

- Meter ruler
- Protractor
- Clamp stand
- G-clamp
- Stop clock
- String
- Mass

Plan

Due to my preliminary work, I have found out that the length of the string is the only affecting factor in this investigation. Therefore, that will be my only variable. In order to find out how length of the string affects the swinging of a pendulum, I will take a result from six different lengths. They will be: 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7 metres.

Conclusion

Factors which may have affected the accuracy of my results include:

- Error in measurement of angle of arc. This angle proved difficult to

measure and it was hard to get the exact same angle for each result. To

improve the accuracy of this measurement, I could have attached the protractor to the clamp stand so that it was in a fixed position. - Error in measurement of string. To improve the accuracy of this, I

could have marked off the points with a pen to ensure they were as

accurately measured as possible. - Human reaction time. Depending on human reaction time, the

measurement period time could have been measured inaccurately, due

to slow reactions when setting the stop-clock etc. This could have been

improved by involving another person to aid me with my experiment

for a quicker reaction time.

In my opinion, if I had to do this experiment again, I would use a computerised pendulum, such as the one which can be found on ‘the pendulum lab’ on the internet. This website has a virtual pendulum, which has the exact measurements for length of string and angle of the arc. This will eliminate any human errors, which will give a more accurate result.

The procedure was relatively reliable, excluding human error, and so I can conclude that my evidence is sufficient to support a firm conclusion that:

The only factor which affects the period of a simple pendulum is its

length. As the length increases, so does the period.

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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