If the couple moment acting on the pipe has a magnitude of 400 n-m, determine the magnitude f of the vertical force applied to each wrench.

A couple moment is produced when a network of forces do not have a resultant force, but only produces moment. As a result, it induces rotation without translation. That means the two forces are equal. 

Moment = Force * Distance

In order to determine the vertical force, we must know the distance between the two forces which is represented by the length of the pipe. Suppose the pipe is 0.5 m, then the force is

400 N·m = F*0.5 m
F = 800 N

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