1. The problem statement, all variables and given/known data Two identical ideal massless springs have unstretched lengths of 0.25m and spring constants of 700N/m. The springs are attached to a small cube and stretched to a length L of 0.30m. One spring on the left and one on the right. An external force P pulls the cube a distance of D = 0.020m to the right and holds it there. Find the external force P, that holds the cube in place. A picture has been attached for reference. 2. Relevant equations Work done on a spring = (1/2)kx22-(1/2)kx12 Work done by a spring = (1/2)kx12-(1/2)kx22 3. The attempt at a solution I tried to compute the amount of work done by each spring and then take that work and divide by double the distance because there are two springs, to figure out the force but I came up with numbers less than one and the answer is supposed to be 28N. I'm not sure if the fact that both springs are already in tension when they were stretched from .25m to .30m and I have to figure in potential energy. It seems that one of the springs, as the block is moved, passes through it's zero force point where as the opposite spring is just stretched further. This passing through the zero point confuses me too. Thank you for any help you can provide.