The vertical bar AB in Fig. C2 has a mass of 150 kg with center of mass G midway between the ends. The bar is elevated from rest at \( 0=0 \) by means of the parallel links of negligible mass, with a constant couple M \( 5 \mathrm{KN} . \mathrm{m} \) applied to the lower link at C. 83. Determine the angular acceleration of the links as a function of \( \Theta \). 84. Find the force \( B \) in the link \( A B \) at the instant when \( 0=30^{\circ} \). The concrete block (Fig. C3) weighing 644 lb is elevated by the hoisting mechanism shown, where the cables are securely wrapped around the respective drums. The drums, which are fastened together and turn as a single unit about their mass center at \( O \), have a combined weight of 322 lb and a radius of gyration about \( O \) of 18 in . If a constant tension \( P \) of 400 lb is maintained by the power unit at \( A \). 85. Determine the vertical acceleration of the block. 86. The resultant force on the bearing at 0 .