warus

I write very simple physics engine for game, which basically simulate springs with mass on end of it. Main problem is to implement all forces which may affect on my mass (because for now i treat spring as object without mass, so forces don't affect on it). What i have already done is gravitation, spring constant and dumping, but it's not enough for me. I want to make it as much realistic as it is possible. So my question is - which forces i forgot to include? What i know, I'm missing limit of spring length. I mean, for now if i have a spring with spring constant 1.0 N/m, length 5 cm, dumping 0.1 (forgot units) and I'll attach to it object with 10kg weight, my spring (by gravitation) will be stretched to 1 m and then it will unstretch, just like nothing happened. I want to allow situation when spring will be stretch so much, it losts it elasticity and it won't be able to oscillate. I think for now it's my main problem. Also in near future i would like to treat spring as object with mass, so it brings another problem - how would gravitation affect on springs shape? I hope that i made myself clear. Sorry for my bad English. Units are in SI system.