Investigate the effect of mass on the extension of a spring.

Extension= New length - Original Length

Prediction:

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

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.

Results Table

Length (cm)

Mass (g)

st

2nd

3rd

Average

Extension

0

2

2

2

2

0

50

2.6

2.5

2.5

2.5

0.5

00

4.5

4.6

4.3

4.4

2.4

50

6.5

6.4

6.4

6.4

4.4

200

8.5

8.3

8

8.2

6.2

250

0

0.1

0.2

0.1

8.1

300

2.2

2.2

2.2

2.2

0.2

350

4

4.1

4.1

4

2

400

6

6

6

6

6

My Method:

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 ruler 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.

Safety:

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.

The following safety precautions must take place:

> Safety googles on. Just incase the spring snaps and the metal flies towards your eyes.

> Make sure your feet are clear from being directly underneath the weights, incase the spring snaps.

> Never overload the spring and never place it on to the other weights.

> Also take care where you put the apparatus on the table put it as far away from the edge of the table as you can.

Fair test:

To make sure this experiment is a fair test we must make sure that the spring characteristics are the same after every result. I must make sure I only change the mass on the spring this will change the extension. I must also make sure I measure the length only when it has stretched as much as it can.

Variable

I will also endeavour to keep the characteristics of the spring the same, such as the spring's original length, the spring's material as well as its thickness. These are called the dependent variable.

Another key fact in keeping this experiment fait is to use the same mass of weights. These weights will each weight at 50g and shall be applied carefully to the spring, as I do not wish to damage or over stretch the spring. After the force has been applied I will wait until the spring its totally stable, as this initiates I will obtain a more accurate and reliable result. By measuring the lengths of the springs carefully using the same method, this will keep my results to the fair test policy.

Scientific Knowledge :

Hooke's Law:

As I explained briefly in my prediction Hooke's law is described in this simple sentence, the extension is directly proportional to the load.

This means when a load is hung from a spring, the length of the spring extends. If the load is increased, the extension increases also.

Conclusion:

From my experiment I have drawn up the following conclusion. I found out that my prediction was correct and that every time I added more weight the spring stretched more, which proves Hooke's law is totally correct, which you can see, in my scientific knowledge.

I also found a pattern in my results which was that every result I gained was an even number, and that most of them went up in the two times tables. I also found out that after I added the last weight it ended in 16 and It was the same all the way through from my 1st reading to the extension.

Evaluation:

Overall I think that my experiment was a success. When I look at my results I see reliable, competent and accurate evidence that my experiment went well. I also know that my experiment went well because by carrying out the experiment 3 times and having an average, which makes for more reliable results.

I have more evidence that my investigation was a success, from my graph I can say I found no anomalous points and it was a complete success.

Although I think my investigation was a success I still think there is room for improvement, I feel I could have found out more about Hookes law to improve and back up my prediction and conclusion.

From this I can confidently say that my experiment was a success.

Michael Demosthenis

Mr Hoy

Physics Coursework