I can't copy the pictures but here's a "reproduction" of one: Wall----------box (There's a spring attached to both the wall and the box.) The box is resting on a frictionless surface. The spring has been stretched to the right by a distance given and it's about to be released. It will proceed to oscillate. We're including only the conservative force of the elastic spring so the mechanical energy is conserved. Rank the figures (there are really 8) from greatest to least on the basis of mechanical energy. I thought I had the right equation for Mechanical Energy (E) : Ei = Ui + Uf and that Uf was 0 so Ei = Ui which is 1/2kx^2 but I'm not getting the right answer. The figures have some-value in N/m over the spring, some-value in meters for the stretch, and the mass of the box in kg. I'm under the impression that the mass of the box has no effect on the mechanical energy. However, I also see this equation E = U + K. Should I be finding U with 1/2kx^2 and K with 1/2mv^2 and adding them? What should I do?