The uniform slender bar of mass m pivots freely about a horizontal axis through O. If th...

The uniform slender bar of mass m pivots freely about a horizontal axis through O. If the bar is released from rest in the horizontal position shown where the spring is unstretched, it is observed to rotate a maximum of 30° clockwise. The spring constant k = 200 N/m and the distance b = 200 mm. Determine (a) the mass m of the bar and (b) the angular velocity ω of the bar when the angular displacement is 15° clockwise from the release position.