We repeated the experiment 3 times to make sure our results were valid. We made sure the experiment was fair by keeping the following variables the same;
Elastic band
Apparatus
Units on metre rule to record results (cm)
Person taking measurement
Amount of load added each time
Person adding and removing weights
Temperature
Position
Lastly, we worked out an average length in cm by adding the 3 results and dividing by 3. We then took 1 average from an other to work out the extension. As seen in the results table over the page.
Conclusion
My graph shows the relationship between the weight on an elastic band and its extension. The graph is not a straight line showing that’s its extension is not proportional to its load, disobeying Hooke’s law. My graph shows that the elastic band has been stretched because the unloading of weights has a greater extension than the loading of weights, and does not return to its original shape.
My graph has shown that an elastic band does not react in the same way as a steel spring because when stretched both react differently. A steel spring keeps its original shape and its extension is proportional to its load obeying Hooke’s law. However, a elastic band stretches and does not keep its original shape, also its extension is not proportional to its load.
Evaluation
There are a few factors I could of changed to improve my experiment to obtain more accurate and clearer results.
First of all I could have repeated my experiment more times to get a more accurate average length to improve my graph. If I were to repeat my experiment I would do it 5 times instead of 3 to get a more accurate length.
Also, smaller weights would of given me a more accurate graph and results, from having smaller weights I would have a clearer idea of how differently a elastic band behaves to a steel spring. If I were to repeat my experiment again I would add only a 0.1N weight each time.
Lastly, I only went up to a maximum of 3N then back down, but with more time available I would of gone up to 6N to test the elastic bands elasticity, strength and to obtain more accurate results to find out exactly how a elastic band behaves.
