Engineering Statics

E-8


A 10 foot boom is acted upon by the 840 pouns force shown. Determine the tension in each cable and the reaction at the ball and socket joint at point A.

The length of each cable is 11 feet from geometry.  A 
FBD of the boom is drawn.
The components of the tension in cable BD are proportional 
to the geometry.
The components of the tension in cable BE are proportional 
to the geometry.
The moment equation about the y axis drawn through point A 
yields the information the the tension in the cables is 
equal.  Looking at the drawing you can see that the geometry 
and the loading are symmetric and therefore you would expect 
the two forces to be equal.
The moment equation about the z-axis through point A 
gives one more relationship for the tensions in the wires.



Substituting in from the geometry proportionality equations the forces are found." >