Two wrenches are used to tighten an elbow fitting. The force F = 10k (lb) on the right wre...

Two wrenches are used to tighten an elbow fitting. The force F = 10k (lb) on the right wrench is applied at (6, –5, –3) in, and the force –F on the left wrench is applied at (4, –5, 3) in.

(a) Determine the moment about the x axis due to the force exerted on the right wrench.

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(b) Determine the moment of the couple formed by the forces exerted on the two wrenches.

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(c) Based on the results of (a) and (b), explain why two wrenches are used.