# Hooke's Law / Young's Modulus - trying to find out what factors effect the stretching of a spring.

## Hooke's Law / Young's Modulus

I am trying to find out what factors effect the stretching of a spring.

Things, which might affect this, are:
· Downward force applied to spring.
· Spring material.
· Length of spring.
· No. of coils in spring.
· Diameter of spring material.
· Cross sectional area of spring.
I have chosen to look at the effect of the weight applied, as it is a continuous variation.
I predict that the greater the weight applied to the spring, the further the spring will stretch. This is because extension is proportional to load and so if load increases so does extension and so stretching distance.

Extension = New length - Original length

To see if my prediction is correct I will experiment, and obtain results using Hookes Law. He found that extension is proportional to the downward force acting on the spring.

Hookes Law
F=ke
F = Force in Newtons
k = Spring constant
e = Extension in Meters

My method of experimentation will be to use a clamp stand and boss clamp to suspend a spring from. A second boss clamp will hold in place a metre rule starting from the bottom of the spring to measure extension in mm. I will then add weights to the spring and measure extension.
Before deciding on the range of experimentation I carried out a preliminary test to find the elastic limit of the springs we had. To do this I added weights to the spring until it did not return to its original shape. This occurred at 12N and so I set a limit of weight to 10N for my experiments. The reason why 11N was not used is that 10 experiments is a more standard number and also that the limit of proportionality is slightly less than the elastic limit of the spring, therefore using 10N ensure I do not exceed the proportional or elastic limit of the spring. I also hope to carry out the experiment 3 times and also take an average to increase the reliability of my results.
Due to the preliminary test no strict safety precautions need to be used, as the only potential danger would be if the spring snapped, however this will not happen if there is no more than the maximum load on the spring of 10N at any one time. This will also remove the problem of the stand on which the experiment is taking place from falling over.

Experiment Diagram

The weights available are 1N masses and so I will take 10 extension measurements starting at 1N up to 10N of force on the spring.

Results Table
Force in N Test 1 Test 2 Test 3 Average
1 33 31 35 33
2 71 75 70 72
3 114 112 115 113
4 150 148 146 148
5 185 183 180 183
6 215 214 212 214
7 250 249 251 250
8 280 280 285 282
9 320 310 315 315
10 355 350 345 350

All measurements in mm

These results are also plotted on a graph on the next page

Now my graph is plotted I can ...