The 10-lb bar is pinned at its center O and connected to a torsional spring. The spring...

The 10-lb bar is pinned at its center O and connected to a torsional spring. The spring has a stiffness k = 5 lb ft/rad, so that the torque developed is M = (5θ) lb ft, where θ is in radians. If the bar is released from rest when it is vertical at θ = 90°, determine its angular velocity at the instant θ = 45°.