Engineering Statics

C-17


Determine the range of values of the tension in wire BC if the magnitude of the couple at the fixed support, D, is not to exceed 100 N-m.

The length of the wire BC can be found from the Pythagorean theorem.
The moment equation at point D allows us to solve for the 
for the tension if we use the moment equal +100 N-m, the maximum 
allowable value.
T can be factored out and the equation simplified.
Further simplification.
Solving gives us one value for the tension.
The same equation is written allowing the moment to be 
-100 N-m.
Following the same simplification procedures as the first 
time allows us to calculate the second value of T.  Note 
that both values of T are positive.  If they come out 
negative you know that you have goofed.