Hey, I am doing coursework for physics (AS level a bit like high school in US) in which we stretched springs in a variety of ways and gathered data and calculated spring constants. As part of the mark scheme i should do extra research in to the theory behind the results. It was suggested that I find out why when doing the experiment it was best to put on the 50g hanger and let the spring stretch a little and put this as zero extension. I searched a lot for the answer but it is hard to get such specific information out of a search engine. Does anybody know why some force is put on and then it is set as zero? I guess it acts differently when completely coiled up and takes a bit to enter the elastic limit. Does anybody know of any good sites or even books on the subject (i dont want to go too deep of course as its just a bit on the side for extra marks)? Thanks very much.