1. The problem statement, all variables and given/known data Two horizontal bars connected by a frictionless pin are released and allowed to fall and impact a fixed pin. Where must the pin impact the bars to ensure rigid body rotation? 2. Relevant equations Conservation of angular and linear momentum, relative velocity equation. 3. The attempt at a solution Pin location: x Initial system velocity: [itex]v[/itex] Left rotation: [itex]\omega_1[/itex] Right rotation: [itex]\omega_2[/itex] Left velocity: [itex]v_1[/itex] Right velocity: [itex]v_2[/itex] Coefficient of restitution was not given, so I assumed a plastic impact, whereby it impacts the pin and rotates with the surface resting against the pin (so, restitution coef = 0). I also don't think gravity matters in this problem, since the impulse force is orders of magnitude greater than the force due to gravity. Meaning: This system could happen independent of gravity, and the pin should be located in the same place. Angular momentum about the pin is conserved. I can also use kinematics to relate [itex]v_1[/itex] and [itex]v_2[/itex] to [itex]\omega_1[/itex] and [itex]\omega_2[/itex]. So, my final equation (initial angular momentum about the pin = final angular momentum about the pin) has three unknowns: [itex]\omega_1[/itex] [itex]\omega_2[/itex] and [itex]x[/itex]. I know that, for rigid body behavior, the two [itex]\omega[/itex] terms will be equal, eliminating one unknown. However, I still have two left. My question is this: Other than angular momentum being conserved about the pin, what other equation do I use to solve for the remaining unknown terms?