Force-extension graph for wool

 It is traditional to use copper wire to explore the force-extension graph for solid materials. The problem is that using the masses that we have, it is very hard to got any results. So I decided to take up the suggestion of using wool. I added 10 gram masses in intervals up to 150 grams.

 I used a set square to avoid parallax error and my rather scrunched up graph is below. I'm going to try this with my class next week because the results being different in loading and unloading is an interesting feature. The problem is the lack of straight section which will make the calculation of the spring constant tricky.