[SOLVED] Conservation of linear momentum and inelastic collision 1. The problem statement, all variables and given/known data I have a homogeneous beam of length L and mass M, attached with a frictionless hinge at one of the endpoints O. The beam is affected by gravity, g, in the negative y-direction. Initially the beam hangs straight down in the negative y-direction. The moment of inertia of the beam for rotations around O in the direction given by the hinge is I. A small bullet of mass m is fired along the x-axis, hitting the beam at the bottom. The bullet has an initial velocity of v0 and remains lodged in the beam after the collision. I have to show that the linear momentum of the system is generally not conserved during the collision. 2. Relevant equations Not quite sure. 3. The attempt at a solution I just can't figure out where to start with this one. Only thing I got so far is that I can't shake the feeling that the hinge must exert a force (centripetal force?) on the beam to prevent it from flying off, so the sum of external forces on the beam is non-zero, ergo no conservation. Any help would be most appreciated.