1. The problem statement, all variables and given/known data Collar A can slide on a frictionless vertical rod and is attached as shown to a spring. The constant of the spring is 4lb/in., and the spring is unstretched when h=12in. Knowing that the system is in equilibrium when h=16in., determine the weight of the collar. Home-made diagram: http://img182.imageshack.us/img182/9642/staticsuc5.th.png [Broken] 2. Relevant equations F=-kx k=4lb/in x=16in-12in=4in F=-kx=-(4lb/in)*(4in)=16lbs 3. The attempt at a solution With the pulley, the spring would still be carrying 100% of the collar's weight. 16lbs for the collar weight can't be the answer, can it? Any help would be appreciated, it's been a while since I've taken a course in physics.