Hello everybody, I'm trying to figure out how to calculate xadd, the additional compression of a preloaded spring (initially compressed of xp) on which a mass is dropped from a height "h". I also wonder : - if the final compressed spring length is the same with or without preload ? - if the spring receive an additional compression xadd >0 whatever the drop height ? (even at h=0.001 ?) I have some remembering about my academic studies (Energy conservation laws applied to spring) but I feel quite uncomfortable since I did not practice for a long time. Thanks a lot for any kind of help.