The Variables
These are the variables that I could change for my investigation.
Length Of String
Mass Of Bob
Angle Of Swing
Preliminary Results
I carried out these experiments so find out which of the variables had the greatest effect on the swing of the pendulum.
From these results I have decided to change the string length because it is the factor which has the greatest effect on the time period of a swing.
Method
First of all, I will set up my equipment making sure that the following are in place.
- The string is held firmly between two pieces of wood to make sure that the pendulum swings from a fixed point each test.
- The clamp stand is firmly on the table so that the experiment will not wobble and affect our results.
There will be a clamp stand holding two blocks of wood with a piece of string in the middle. There will be a bob weighing one gram at the end. This mass will remain constant. The length of the string is the variable that I am changing. I will measure the length of the string using a ruler. The lengths that we are using are 0.05cm, 0.10cm, 0.15cm, 0.20cm, 0.25cm, 0.30cm, 0.35cm, 0.40cm, 0.45.cm and 0.50cm. The angle of swing will be 15° and will remain constant.
Diagram
This diagram shows how my equipment was assembled for my preliminary results and how it will be for my main experiment.
I found out the averages of all of my values, divided them by 10 to get the average time for one swing and squared that number to create T2
Analysis
The graph that I have drawn is a linear graph. It shows that as the length of the string increases, so does the time needed for one complete oscillation. My graph shows that T2 is proportional to the length of the string. Eg. Length of string = 0.25cm and time taken = 1.00 second.
This is because the mass at the bottom of the pendulum has further to travel. The string length has the greatest effect on the swing because as it is increased, the bob has to travel further. The angle of swing does not affect the time period because the bigger the angle, the faster the bob falls but this is slowed down because there is greater air resistance. The same applies to the mass of the bob. It will fall at a faster rate but be hindered by air resistance.
This is the equation I used to out the time of one swing.
T=2π √l/g T=time l=length g=gravity
Gravity= 9.8m/s2
We need to square T so that the graph is linear. When the equation is rearranged it becomes.
T2 = (4π2/g)l Rearranged equation to find out the accuracy of gravity m/s2
We can use this equation in a straight line graph. Y=mx +- c m= gradient of the line
T2 =y
(4π2/g) = m → This value always remains constant
Evaluation
