Pendulum Investigation

Physics

PENDULUM INVESTIGATION

Aim of the investigation

The aim of the pendulum investigation is to see what will happen if I change a variable whilst I swing a pendulum and see the effect which it has on the pendulums time to complete one whole swing (from where it starts, to the opposite end, and back again). This will give me an insight into what will effect the time of the swinging of the pendulum, be it weight, string length, the angle, or the swinging point.

Planning my investigation

I will set up my investigation by having a 30cm length of string. This will be cut six times as I am measuring six different lengths of string. These will include lengths of: 30, 25, 20, 15, 10 and 5 centimeters. To make my results reliable I will test them three times each, at all the lengths, and average them out, to give a more accurate measurement. I think that I can produce reliable, precise results, using this information and plan. I will have enough data to spot "misfit" results too.

Safety Issues

For safety, I will use a pair of safety goggles. This is because whilst the pendulum is swinging, it may hit me in my eyes, as the pendulum is at a similar level of height to my head.

I will also clear all the chairs, coats and bags from the vicinity as they may cause obstruction to me, other people who I work with, or people passing who may be injured.

After taking these measures into account, I was able to proceed to the next stage of the gathering of results.

Fair testing

I will make my testing as fair as I can by firstly, making sure that the windows are closed so there are no elements affecting my pendulum, before I begin the investigation. Secondly, I will then measure the piece of 30cm string and the weight of the pendulum to double check on my first readings. Thirdly, I will use a protractor to measure exactly 90Ñ" of where to swing the pendulum from. And finally, I will measure ten swings and the time it takes to complete them. This is because it is easier to count the length of ten swings than it is to count the length of one swing. I will then divide my answer by ten to show the result for the length of one swing.

My prediction of the test results

I believe that the events which will occur are that the longer the piece of string which holds the weight, the longer the time it takes the pendulum to complete one whole swing. So the shorter the string length, the faster the time for the pendulum to fully complete a full swing, as it has less distance to attain.

For my investigation I will use:

- One piece or 30cm string - to be used as the length of the pendulum

- One 17g piece of plaster-scene - as a weight, to swing the pendulum

- A Stand - to hold all of the equipment on

- A G-clamp - to hold the stand in place

- Safety goggles - to protect my eyes

- A stopwatch - to record the swing length of the pendulum

Key Factors

The key factors which are involved in this experiment are the swinging angle of the pendulum, the swinging height which the pendulum will be released from on each experiment and the weight which will go on the end of the string to form the complete pendulum. The other effects such as wind are negligible and will not affect the experiment in any noticeable way.

Factors I will change

The variable which I will change is the length of the string which holds the pendulum. I will change the length of the string from 30, 25, 20, 15, 10 and 5 centimeters. This will give me a good indication of what effects the length of time which a pendulum takes to make one complete swing, and a reasonably large range of results to analyse.

Controlled Factors

I will control most of the factors (string length, height dropped from, weight and the swinging angle). The factors which I will not control are the effects of gravity on the pendulum and the resistance of the air on the swinging.

Factors involved in predicting

I will take into account the string length and the weight of the pendulum. These two factors will be the basis of my prediction. This is because the longer the string, the longer the distance is to complete the full swing of the pendulum. (Illustrated in the diagrams below)

[ Picture of large string length swinging ]

[ Picture of small string length swinging ]

The weight of the pendulum will also affect the time for the pendulum to complete a full swing. This is because the less the weight, the faster something will move through the air and the heavier it is, the more resistance it creates.

Range of results

My range of results are gathered by using a string of a variable lengths from 5cm - 30cm. The test will be repeated three times to obtain a more accurate reading. I will swing the pendulum from an angle of 90Ñ" which I will measure using a protractor. This will give a constant variable of the angle which it is swung from so one time the pendulum is not swung from a higher point or lower point to the others.

In order to record these results accurately, I have recorded the amount of time it takes for ten swings, rather than one swing, as it is easier to count ten swings if each swing is only a half a second long, so I will just divide the total of ten swings by ten to give me the result of one swing. These results are recorded in the table below:

String Length Test 1 Test 2 Test 3

30cm 1.3 1.3 1.4

25cm 1.2 1.1 1.5

20cm 1.0 0.9 1.1

15cm 0.9 0.7 1.0

10cm 0.7 0.6 08

5cm 0.5 0.5 0.6

The results are shown for one complete swing