Fair Testing
- As the experiment is repeated three times, to make it fair the same type of spring will be used each time.
- The same person will measure the extension each time.
- Measuring will take place at eye level so precise and accurate results can be taken. Also this ensures that the reading of the extension is taken at the same place and level to make it a fair test. Also a setsquare will be used to get precise and accurate results as I can line the spring up with the metre rule to read off the extension.
- Each spring will have to be the same length.
Safety
- Normal lab rules apply (hair tied back, ties tucked in etc…)
- There is a danger that when too many weights have been added to the spring that the spring will uncoil, drop its weights and spring into the air therefore goggles must be worn to protect eyes from spring.
Prediction
Hooke’s Law states that the extension is directly proportional to the stretching force”. In this case the extension of the spring is directly proportional to weights added so therefore the results in this experiment should draw up a straight line through the origin. But this is only valid up to a certain point.
I will show what happens using a graph and diagrams:
Ext B
(Cm)
P
E
O F (N)
When a ductile material is stretched it obeys Hooke’s Law up to the limit of proportionality marked E on the graph. If the material is stretched further up to its elastic limit marked P, when the force is removed it will still return to its original length. But if stretched beyond point P it will no longer return and suffer deformation. If stretched yet again further it will eventually brake at B. From O to P the material stretches elastically and atoms are nearly pulled apart. From P to B the atoms start to come apart then finally brake at B.
no force force applied more force applied
(O to P) (P to B)
So from this scientific knowledge I predict that the extension of the spring will be directly proportional to the weights added but only up to a certain point. Then after this point the last extension will increase more than usual because at this point the atoms are breaking so there is one last bigger extension given at the end before the spring brakes.
Obtaining Information
Method
- The following apparatus was used in this experiment:
Clamp stand
3 springs (all the same type)
Metre rule
100g weights
Goggles
- The apparatus was set up as follows:
The clamp stand was put on the table and a spring was attached to the clamp securely.
- A 100g weight was added to the spring and the extension of the spring was measured using a metre rule. Precision and skill was used to obtain accurate and reliable results as the extension was taken to the nearest millimetre and the reading was read from eye level using a setsquare.
- This was repeated until the spring broke. Before this point goggles were worn to ensure safety from the flying spring after it broke. A cushion of some sort was placed beneath the weights before the spring broke. So when the spring did brake the weights had a cushioned fall
- This method was repeated two more times with the same type of springs. This was because then an average could be taken and hence a more accurate graph.
- A results table and graph were drawn up.
Results Table
Analysing Information
Conclusion
Basically I found out in this experiment that:
- The more weight added the more the spring stretched.
- The graph was a straight line through the origin up until the little curve at the end.
-
The straight line confirmed that the extension was directly proportional to the stretching force (i.e. the weights) for that part of the graph only though. Direct proportion means that if you double the force the extension will double.
- The elastic limit was
- The little curve at the end of the graph shows where the last extension taken (before the spring broke) had increased more than the normal extension. This proves that at this point the spring becomes stretched past its elastic limit and the atoms in the spring are about to be fully pulled apart until they do right at the end of the graph.
The results graph shows that all of the results were in the line of best fit. My graph produced a straight line through the origin with a little curve at the end. This shows that my results for this test support Hooke's Law well, which proves my prediction to be correct. As I predicted the extension increased in direct proportion to the weights being added until a certain point. And after this point the extension increased higher than normal giving the graph a little curve at the end.
In conclusion I am pleased with my results and feel they support each other as well as the laws they were based on. I have enjoyed doing this experiment as I have learned a lot in doing so.
Evaluating Information
Evaluation
I think the evidence I have obtained is accurate and reliable as Hooke’s law can support my results as my prediction was right and my prediction was based on Hooke’s Law.
I think the procedure I used was fairly accurate, as I made sure I made it a fair experiment. Also I used precision and skill to obtain my results (I did this by using a set square at eye level and reading the extension to the nearest millimetre).
I think the quality of the evidence is good as I didn’t have any anomalies in my results and Hooke’s Law supports my evidence obtained (results).
The method I used could have been performed better and more accurately in more time. I could of taken longer to do the measuring of extension to get more precise results. Also
I could have improved this experiment by testing more than three springs to get a more accurate average and therefore a more accurate graph.
Here are some suggestions for further investigation work and experiments that could be lead or followed on from this experiment:
- An experiment to find out if the extension of spring is affected by its material. So several different types of material of spring could be used e.g. copper, steel, etc…
- Different lengths of springs could be tested to find out and to compare results to find out if there is a pattern between the size of the spring and its elastic limit or where at what extension the spring breaks.
- Different sized springs and different strengthened springs could be also tested in the same way to see if there is a pattern or comparison between the size increase and the elastic limit of the spring.
Physics
Investigation on factors that affect the resistance of a metal wire
Steven Anderson
By Steven Anderson