14(3). The system shown in Fig. 12-10 is inequilibrium. Find (a) the tension T in the cable and(b) the force exerted on the strut S by the pivot P. The strut weighs 100 lb. I just used the sum of component forces at the maxis ( top ofthe crane ) and not one torque equation ? ( T = 448.2877 lb ; Px = 387.69 lb ; Py = 387.69 lb ...? ) This is not the correct answerbecause I did not consider all the torques ( if I had room I woulddraw the free-body diagram for the new answers I have --> T = 687.33 pounds ; PX = - 1,019.51 pounds ; PY = - 943.665 pounds .)
Explanation / Answer
No. You need the torques. . It's simple logic: there are three unknowns(Px Py and tension in the leftcable). So you need three equations: . sum of horiz forces onstrut sum ofvert forces onstrut sum oftorques on strut . That's it... if you were able to solve for three unknowns withonly two equations, you are creating new mathematics. You shouldpublish and collect your Nobel Prize.