Angular acceleration, rigid body

[usn7564]

Homework Statement

A circular disk with the mass m and radius r is hanging from two ropes with length l when suddenly the rope ED snaps. For this moment, find:

a, The angular acceleration for the rope OB, the angular acceleration for the disk
b, The force T acting in OB

The Attempt at a Solution

Or lack thereof, really don't know how to approach this without a given ω. I can find some relations between the accelerations at different points but ultimately I'm sitting with a lot of unknowns.
Frankly don't know how to connect the force acting on the disk to any general acceleration.

 

[ehild]

You know the angular speed at the instant when rope ED snaps: the disks is in rest.
The disk is a rigid body: all points have the same angular acceleration and angular velocity. How is the angular acceleration of a rigid body related to other quantities - torque and moment of inertia? ehild

 

[haruspex]

I can find some relations between the accelerations at different points

So post them.
What forces act on the disk?