Frames and Machines $(16$ points$)$

The pumping unit is used to recover oil enabled by the motion of

the arm AD causing the walking arm AC to rotate about the pivot

point at $B.$ When the walking arm $AC$ is horizontal, the force in the

cable acting at the well head is $250lb.$ The head at $C$ weighs $60lb$

and has a center of gravity at $G_C.$ The walking arm $AC$ has a weight

of $130lb$ and a center of gravity at $G_B.$

Determine the force in the rod $AD$ at the instant shown. Be sure

to show the free body diagram used and identify any two$-$force

members acting in your free body diagram.