Physics: time period of a pendulum.

GCSE Science

physics: time period of a pendulum

PLAN:

String

Ruler
B A Weight

Stand

Desk

Timer

The time period for a pendulum is the time taken for the pendulum to swing from one point to another (i.e. from A to B and back again)
I need to record this time period, but it is too short, so I will time 10 periods and then divide the final time by 10 to give me the time of one pendulum time period.
When doing this experiment I will need to take in account the three variables; Displacement, the mass of the pendulum, and the length of the string that the pendulum is attached to. I have decided to vary the variables in the following way:

Displacement (0)
80
20

Length Of String (cm)
80
20

Mass Of Pendulum (g)
200
500

I have chosen to use this figures because they are wide apart and I will find out how many figures I will need to use in my final experiment.
In my preliminary experiments I am only going to vary one variable at a time, when I use mass as a constant I will set it as 100g, this is because it is not too small a value and it is not too big. When I set length of string as a constant I will 60 cm, this because it is an average value. When I set displacement as a constant I will set it as 50 degrees, this is because I tested 90 degrees and it was too big a displacement so I lowered the value to 50 degrees. I will time 10 time periods, as I said before, and divide the answer by 10 to give the time of one time period.
Here are my preliminary results:
PLAN:

Displacement (0) Time Period (s)
80 2.15
20 2.15

Mass (g) Time Period (s)
200 2.16
500 2.14

Length Of String (cm) Time Period (s)
80 1.8
20 1.2

This is a preview of the whole essay

Displacement (0) Time Period (s)
80 2.15
20 2.15

Mass (g) Time Period (s)
200 2.16
500 2.14

Length Of String (cm) Time Period (s)
80 1.8
20 1.2

By looking at my preliminary experiment results I can say that the displacement and the mass of the pendulum will have no effect on my final experiment results. I can also make a prediction of my final results:
"The longer the piece of string, the longer the time period of the pendulum"
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. The longer the piece of string the higher the potential energy, so the velocity will be greater. In my final experiment I am going to use the following values for the length of the piece of string:
100, 80, 60, 40, 20 (cm) lengths
with a mass of 100g acting as the pendulum, and the displacement length I am going to use is 50 degrees. I have chosen to use these values because the lengths are spread out, and the displacement was too high at 90 degrees so I lowered it and the mass is neither a very large mass nor a very small mass. I am going to time 10 time periods, because 1 is too small, and then divide the time by 10 to give me the time of one time period.
I will repeat the above experiment 3 times and take an average of the 3 sets of results. To find the average I will need to do the following calculation:
Average = RA + RB +RC
3
Where RA = Result A
Where RB = Result B
Where RC = Result C

OBTAINING EVIDENCE:
Results A
Length Of String (cm) Time Period (s)
100 2.0
80 1.8
60 1.6
40 1.3
20 1.2
10 0.9
Results B
Length Of String (cm) Time Period (s)
100 2.1
80 1.8
60 1.5
40 1.3
20 1.1
10 0.9
Results C
Length Of String (cm) Time Period (s)
100 2.1
80 1.6
60 1.5
40 1.4
20 1.0
10 0.8

As you can see from my three final experiment results I have repeat values, they are highlighter in the same colour if they are matching
I am now going to take an average of my 3 sets of results:
Length Of String (cm) Time Period (s)
100 2.07
80 1.73
60 1.53
40 1.33
20 1.1
10 0.87

ANALYSING EVIDENCE AND DRAWING CONCLUSIONS:
As you can see from my graph, I can say that there is a relationship between the length of the string and the time taken, this relationship is:
"The longer the piece of string, the more time it takes it takes for the pendulum to swing"
I can say that the prediction matches my analysis, so my prediction was correct. My Graph shows that I have done the experiment correct because there are no extreme pieces of data or faults in the graph.

EVALUATING EVIDENCE:
My results show that, as the length of the string increased, the time increased.
I can say that my results are accurate because I have taken the time of ten time periods of the pendulum, I have done this to keep my results accurate. To make it more accurate, I did the experiment 3 times and took an average of the 3 results I got for each length of string. This also proves that my results are realistic.
My experiment could be improved by using more lengths of string, which would give me more results, which would give me a clearer graph.