A 70kg rectangular door measures 1.2m wide by 2.3m tall. It closes automatically using two hinges with torsional springs mounted on the vertical edge of the door. The springs each have a torsional stiffness of M = 50θ Nm where θ is measured in radians. If the door is released from rest when it is open at θ = 90°, determine its angular velocity at the instant θ=0°. Treat the door as a thin plate.