*17-68. The door will close automatically using torsional springs mounted on the hinges. If the torque on each hinge is M = k0, where 0 is measured in radians, determine the required torsional stiffness k so that the door will close (0 = 0) with an angular velocity w = 2 rad/s when it is released from rest at 0 = 90. For the calculation, treat the door as a thin plate having a mass of 70 kg. 0.4 m 1.5 m M B 0.4 m M A 1.2 m