The vertical bar AB in Fig. C$2$ has a mass of $150$ kg with center of mass G midway between the ends. The bar is elevated from rest at $\backslash (0=0\backslash )$ by means of the parallel links of negligible mass, with a constant couple M $\backslash (5\backslash$mathrm$\{$KN$\}.\backslash$mathrm$\{$m$\}\backslash )$ applied to the lower link at C$.$

$83.$ Determine the angular acceleration of the links as a function of $\backslash (\backslash$Theta $\backslash ).$

$84.$ Find the force $\backslash ($ B $\backslash )$ in the link $\backslash ($ A B $\backslash )$ at the instant when $\backslash (0=30^\{\backslash$circ$\}\backslash ).$

The concrete block $($Fig$.$ C$3)$ 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 $\backslash ($ O $\backslash ),$ have a combined weight of $322$ lb and a radius of gyration about $\backslash ($ O $\backslash )$ of $18$ in $.$ If a constant tension $\backslash ($ P $\backslash )$ of $400$ lb is maintained by the power unit at $\backslash ($ A $\backslash ).$

$85.$ Determine the vertical acceleration of the block.

$86.$ The resultant force on the bearing at $0.$