$2/157$ The slotted disk sector rotates with a constant counterclockwise angular velocity $=3ra\frac{d}{s}.$ Simultaneously the slotted arm $OC$ oscillates about the line $OB($fixed to the disk$)$ so that $$ changes at the constant rate of $2ra\frac{d}{s}.$except at the extremities of the oscillation during reversal of direction. Determine the total acceleration of the $nA$ when $=30$ and ${}^{}$ is positive $($clockwise$).$

Ans. $a=1\mathrm{.}060\frac{m}{s^2}$