Hello everyone. I'm burning my head at this one, maybe someone could offer some insight? Here's the deal: imagine two masses, m1 and m2, united by a massless spring, of lenght l (relaxed). m1 | | _ > spring, at lenght l (relaxed) | ___m2____ ground The system has this config at rest. Then, it'f given a velocity v , upward, to the mass m1, and the question is: what is the position of the masses in any given time? I've figured out that I've to break the problem in two parts: find out the center of mass motion and then determine the position of the masses relative to it. However, how can I do that? I've already found out the center of mass motion, but I can't find the position of the masses relative to it. I assume it's a oscillatory motion, but I can't find it's amplitude. The only thing I have is the initial velocity of the mass m1, nothing else. Please, any advice would be HIGHLY useful hehehe Thanks in advance!