1. The problem statement, all variables and given/known data The system depicted in the attachment consists of a slender rigid link of mass m1 hinged at point O, and supported by a spring of stiffness k2 (200N/m) at point B. The link in turn supports a spring of stiffness k1 (400N/m) at point A connected to a point mass m (2kg). Determine the equations of motion for the link hinged at O, and the point mass m relative to the static equilibrium of the system. Develop the general equations of motion, and linearise this result for small angle approximations of the link displacement such that sin (theta) ~= (theta) and cos(theta) ~= 1 (valid for angles up to 5 deg). 2. Relevant equations 3. The attempt at a solution I haven't gotten very far with this because I don't know how to start solving it. I've come up with the position vector for the mass m, which is: 0.2 cos (theta) i - (0.2 sin (theta) + mg/k) j and I've tried to do the summation of moments about point O, getting Mo = 2g cos(theta) - 200*x2 *cos(theta) [x2 is the spring compression/extension, not x^2] and right about here I get stuck, because I have no idea how to proceed on :( Any help would be great, I just need to know what are the relevant equations I can use for this.