1. The problem statement, all variables and given/known data A rod of length L and mass M can rotate respect to an articulation fixed to the wall. The other extreme of the rod is attached to a spring of constant k. When the system is in equilibrium the rod keeps horizontal. Find the angular frequency for small oscilations respect to that position. 2. Relevant equations 3. The attempt at a solution My idea is to get to the differential equation by using Newton or Energy equations but I need a boost to do this because I am not sure where the forces are pointing at. I know the articulation does a force but where does it point at? And the spring? Any help will be really really appreciated!