Deltoid Muscle A crossing guard holds a STOP sign at arm's length, as shown in the figure(Figure 1). Her arm is horizontal, and we assume that the deltoid muscle is the only muscle supporting her arm. The weight of her upper arm is Wy = 16 N , Find fa. the weight of her lower arm is Wi = 18 N , the weight of her hand is Wh = 4.0 N , and the weight of the sign is W= = 8.4 N . Express your answer using two decimal places. The location where each of these forces acts on the arm is indicated in the figure(Figure 2). A force of magnitude fa is exerted on the humerus by the deltoid, and the shoulder joint ? exerts a force on the humerus with horizontal and vertical components given by f, and fy, respectively. (The weights in the figure are drawn to scale; the unknown forces are to be fd = KN determined. If a force is found to be negative, its direction is opposite to that shown.) Submit Request Answer Figure