1. The problem statement, all variables and given/known data Two springs each have a spring constant k and equilibrium length l. They are both stretched a distance l and attached to a mass m and two walls. At a given instant the right spring suddenly changes its spring constant to 3k. What is the resulting x(t)? Take initial position to be x=0 Basically 2 springs stretched between 2 walls with mass m in the middle and a spring constant suddenly changes to 3k. 2. Relevant equations I imagine I just have to get the equation for force and solve the resulting differential equation. 3. The attempt at a solution I started out drawing a diagram and each spring is exerting a force of k*l in opposite directions. When the spring constant changes the net force is equal to 2k*l towards the right. I cant seem to get F in terms of x though. Any help is appreciated.