As shown below, a uniform disc is mounted to a fixed axle and is free to rotate without friction. A thin uniform rod is rigidly attached to the disc so that it will rotate with the disc. A block is attached to the rod.
Disc : mass = 3m, radius = R, moment of inertia about center ID=32mR2
Rod : mass = m, length = 2R, moment of inertia about one end IR=43mR2
Block : mass 2m
The system is held in equilibrium with the rod at an angle θ0 to the vertical, as shown above, by a horizontal string of negligible mass one end attached to the disc and the other to a wall.
The tension in the string is