A bathroom door, which is 0.91 m wide and 2.13 m high, is equipped with a torsional spring and a torsional (rotational) viscous damper so that it automatically returns to its closed position after being opened. The door has mass of 60 kg and a centroidal moment of inertia (about an axis parallel to the axis of the door's rotation) of 7.2 kg-m2. The torsional spring has a stiffness of 25 N-m/rad.
- What is the damping coefficient (in N-m-sec) such that the system is critically damped?
- A man with an armload of packages, but in a hurry, kicks the door to cause it to open. What angular velocity (in rad/sec) must his kick impart to cause the door to open 70 degrees?
- How long (in sec) after his kick will the door return to within 5 degrees of completely closing?
- Repeat questions (a)-(c) if the door is designed with the damping ratio, l=1.3.