How the extension of the spring will change or vary, when force is applied.

Diagram

Method

* Set up all the equipment as shown in the diagram

* Add chosen weights to the spring

* Record you results

I will need to take the readings for loading and unloading of the weights because then I can see the extension of the spring.

I will check that I have not exceeded the elastic limit by measuring the spring before I put on a different weight to see if the length has got longer.

The springs need to be completely still, if it is swaying you will not be able to measure the distance accurately

The weights should be added carefully. If you just drop the weights on then more force would be applied and this could cause it to go passed the elastic limit.

I will calculate the extension by taking the initial length of the spring away from the final length of the spring.

I plan to take 8 or 10 readings of the length and weight over a wide range of values.

Prediction

I predict that if you double the load, it doubles the extension and if you put on 3 times the load it will treble the extension. I predict this due to Hooke's Law.

Hooke's law is when:

The extension is directly proportional to the stretching force

Due to this law I predict that when I plot a graph of showing the extension, it will go up in a straight line. When it reaches its elastic limit then it will curve.

Results Table

Mass of load

Weight of load

Initial length of spring (cm)

Final length of spring (cm)

Extension (cm)

0

0

3.2

3.2

0

0.1

3.2

7

3.8

0.2

2

3.2

0.6

7.4

0.3

3

3.2

4.3

1.1

0.4

4

3.2

8

4.8

0.5

5

3.2

21.5

8.3

0.6

6

3.2

25.3

22.1

0.7

7

3.2

28.7

25.5

0.8

8

3.2

33.5

30.3

Graph results

The graph shows that the gradient is positive as it is going up. This means that the extension increases every time. It increases by nearly the same amount every time. You can tell when it has gone past its elastic limit when it starts to go up instead of going in a straight line.

e.g.

At point P the elastic limit has been lost.

Trends and patterns

When I add weights to the spring it extends to an average of 16.6cm.

Analysis and Conclusion

When a weight is added to the spring, it extends but when you get to a certain weight (force) the elastic limit exceeds. The spring then becomes permanently deformed.

Every time a weight was added the spring was extended by an average of 3.7cm for all the weights.

Because we know how much it increases by we can find the extension of the spring without actually adding on any weights.

If you multiply the weight of the load with the average extension that is 3.7 you will get the extension for that weight.

E.g.

2 x 3.7 = 7.4

4 x 3.7 = 14.8

This means that the extension is directly proportion to the force, it proves that Hooke's law is correct.

Evaluation

I thought that the method I used was quite accurate because I got the right results and I managed to prove Hooke's law. The experiment did not take too long to do.

In my results I only had one anomalous result. This was for 8N because I got 4.8 for the extension whereas all the rest were in between 3.4cm and 3.8cm. I think this is becauseit was losing its elastic limit.

To make the results more accurate I could put a pointer on the end of the spring so I would be able to read the results more accurately.

I should have done each experiment three times and then found the average, this would have been more accurate instead of just doing it once.

Even though I did not do these things to make it more accurate, my results were reliable enough.

Further work

I could use different springs like copper, brass or anything. I would compare the forces required to stretch them and see which spring was the best and which would exceed its elastic limit first.

Harpreet Sekhon