how did they dervie angular velocity

I = 3kg x (0.03m) = 0.027kg . m Now, we can write the conservation of energy equation as follows: 1.769J = -1.5kgv2 + 20.027kg - m @2 Solving for w, we get: 1.769.J (0.027kg-m ) = 11.57 rad Therefore, the angular velocity of the bar as it passes through the vertical position is 11.57 rad/s