1. The problem statement, all variables and given/known data The 2-lb collar C fits loosely on the smooth shaft. If the spring is unstretched when s = 0 and the collar is given a velocity of 15 ft/s, determine the velocity of the collar when s = 1 ft. 2. Relevant equations F = kx 3. The attempt at a solution x = l-l0 = (√[1 + s2] - 1) ft Fsp = kx = [4√(1 + s2) - 4] lb So, now I've found the spring force, how does velocity fit into this?