Assuming = 60 in Prob. 3.122, replace the two 40-lb forces with an equivalent force-couple system at D and determine whether the plumber's action

Assuming θ = 60° in Prob. 3.122, replace the two 40-lb forces with an equivalent force-couple system at D and determine whether the plumber's action tends to tighten or loosen the joint between

(a) Pipe CD and elbow D,

(b) Elbow D and pipe DE. Assume all threads to be right-handed.

PROBLEM 3.122 In order to unscrew the tapped faucet A, a plumber uses two pipe wrenches as shown. By exerting a 40-lb force on each wrench, at a distance of 10 in. from the axis of the pipe and in a direction perpendicular to the pipe and to the wrench, he prevents the pipe from rotating, and thus avoids loosening or further tightening the joint between the pipe and the tapped elbow C. Determine

(a) The angle θ that the wrench at A should form with the vertical if elbow C is not to rotate about the vertical,

(b) The force-couple system at C equivalent to the two 40-lb forces when this condition is satisfied.

40 lb 40 Ib 10 in 10 in 7.5 in 7.5 in 25 in. 18 in