Answer
(a) 2640 psi. (b) 2320 psi.
Work Step by Step
(i) if angle = 0;
draw free body diagram of rod CEF(fig.1);
Now apply conservation of angular momentum about point c;
we get;
F*12 - 60*16=0
=>F=80ib;
Now, 80ib force is acting at E in upward direction so its reaction which is equal to -80ib is acting on rod ED(fig.2);
since stress =P/A;
=-(80/(1/8))
= -640psi.
for part (b);
also draw FBD(use fig. 3;)
Now apply conservation of angular momentum about point c;
in this case we get
60*8-F*12=0
F=40ib;
stress =-F/A;
=-40/(1/8)
=-320psi.
