1. The problem statement, all variables and given/known data I have 2 walls, 3 springs, and two masses. The masses and springs are not necessarily similar to the other(s). They are connected in a configuration: Wall-Spring1-Mass1-Spring2-Mass2-Spring3-Wall. I need to find equation for both masses, given that not all springs are in equilibrium when the system is set into motion. Assume that for this system, there is one scenario in which the system is in its equilibrium state. In this state, x_1 and x_2 (defined below) are 0. Springs constants: k_1, k_2, k_3 Masses: m_1, m_2 Displacement of mass 1 from equilibrium: x_1 Displacement of mass 2 from equilibrium: x_2 2. Relevant equations F = -kx U = 1/2 * kx^2 K = 1/2 * mv^2 E = U + K dE/dt = 0 (closed system) 3. The attempt at a solution I first calculated the forces on each mass for a given position and found that F_1 = -k_1 * x_1 - k_2 * (x_1 - x_2) F_2 = -k_3 * x_2 - k_2 * (x_2 - x_1) Also, E = 1/2(∑kx^2 + ∑mv^2) (' denote derivative with respect to time) and dE/dT = k_1*x_1*x_1' + k_3*x_2*x_2' + k_2*(x_1 - x_2)(x_1' - x_2') + m_1*x_1'*x_1'' + m_2*x_2'*x_2'' = 0 But I'm not sure what to do from here. First, are my equations for force correct? The middle spring (#2) applies the force F=-kx to two objects and I have only ever dealt with springs fixed on one end so I'm not sure. Also the dE/dT = 0 is a nonlinear differential equation and I have only ever dealt with linear differential equations so I don't know how to solve it. Would this be better in Physics hw help? I posted here since it is hw for a DE course.