1. The problem statement, all variables and given/known data When a .5kg mass is suspended from a spring, the spring stretches 4cm. The mass is then displaced 2cm from its equilibrium position and released. (a) What is the spring constant? (b) What is the mechanical energy of the mass? (c) What is the speed of the mass as it passes through its equilibrium position going down and going up? 2. Relevant equations F=kx (k is spring constant) W= .5(k)x2 KE= .5mv2 3. The attempt at a solution For part A I used F=kx: mg=kx (.5kg)(9.8m/s2) = k (.04m) k= 122.5N/m For part B I used W= .5kx2: W= .5(122.5N/m)(.02m)2 W= .025J For part C I used KE = .5mv2 .025J = .5(.5kg)v2 v= .32m/s I just need to make sure that I'm on the right track with this problem. I can get confused as to when to use .04m and .02 and generally with using formulas.