Question

3.121 as an adjustable brace bc is used to bring a wall into plumb, the force - couple system shown is exerted on the wall. replace this force - couple system with an equivalent force - couple system at a if r = 21.2 lb and m = 13.25 lb·ft.

Explanation:

Step1: Identify the given values

$R = 21.2$ lb, $M=13.25$ lb - ft

Step2: Recall force - couple system concept

The force - couple system at a point is equivalent to the original force - couple system acting on the structure. Here we are not asked to perform a specific calculation (like finding components etc), but if we assume we want to keep the equivalence at point A, the force $R$ and couple $M$ remain the same in the equivalent force - couple system at A.

Answer:

The equivalent force - couple system at A has a force $R = 21.2$ lb and a couple $M = 13.25$ lb - ft.