Here's the scenario: A uniform stick of length L and mass M lies on a horizontal surface. A point particles of mass m approaches the stick with velocity v on a straight line perpendicular to the stick that intersects with the stick at one end. After the collision, the particle is at rest. My question is, the angular momentum should be conserved in this system right? After the collision, the stick will gain angular momentum as it will be rotating (as well as translating) after the collision. But initially, the particle could either have or do not have angular momentum depending on whether the particle is rotating. Assuming that the particle does not rotate, then the particle should not have any angular momentum. Then in this case how is the angular momentum conserved? The initial angular momentum would be zero initially and non-zero after the collision right? "The law of conservation of angular momentum states that when no external torque acts on an object or a closed system of objects." In this case the torque is an internal torque in the particle-stick system right? Please help thanks.