1. The problem statement, all variables and given/known data "A coil spring has a force constant of k = 4.0 lb/in. When the spring's axis is inclined at an angle 30 degrees from the horizontal, a W = 2.0 oz ball is propelled to a height of 6.0 ft. By how much must the spring have been compressed initially? (1 lb = 16 oz) 2. Relevant equations *PE = Potential Energy *KE = Kinetic Energy PEi = mgh KEf = 0.5mv^2 F = ma F = -kl 3. The attempt at a solution So, I set PEi = KEf mgh = 0.5mv^2 v^2 = mgh / 0.5m v = SQRT(2gh) v = SQRT(2 * 32.2 ft/s^2 * 6 ft) v = 19.7 ft/s Now, I'm just really confused. I don't know how to go farther than this. I'm figuring that Vf = 0 ft/s (at the topmost point) but I don't know much more than that. I'm assuming that acceleration = gravitational constant, but I'm not really sure where that gets me. In the end, finding the velocity seems kind of useless. Unless you can just set F = ma = -kx, but I'm not sure whether I can actually do that, seeing how the spring is at an angle... Someone tried to explain this to me and told me that I'm calculating this all wrong because I'm not taking into account horizontal vs. vertical PE and KE, so I'm even more utterly lost. Any help would be appreciated.