A wad of clay of mass m1 with an initial horizontal velocity v1 hits and adheres to the...

A wad of clay of mass m₁ with an initial horizontal velocity v₁ hits and adheres to the massless rigid bar which supports the body of mass m₂, which can be assumed to be a particle. The pendulum assembly is freely pivoted at O and is initially stationary. Determine the angular velocity of the combined body just after impact. Why is linear momentum of the system not conserved?