48 CHAPTER 2 Basic Operations with Force Systems 3ft 6 ft 240 N 300 N 25° -1.2 m 1.2 m Fig. P2.18 120 lb 30 ft T3 Fig. P2.17 2.17 The trapdoor is held in the horizontal plane by two wires. Replace the forces in the wires with an equivalent force R that passes through point A, and determine the y-coordinate of point A. 2.18 Replace the three forces acting on the guy wires by a single, equivalent force acting on the flagpole. Use T₁ = 200 lb, T₁ = 400 lb, and T3 = 350 lb. 2.19 The three forces acting on the pole are equivalent to a single force R. Determine (a) the magnitude of R; and (b) the coordinates of the point where the line of action of R crosses the xy-plane. 2.20 The three forces, each of magnitude F, are applied to the crate. Deter- mine F so that the three forces are equivalent to a single 600-lb force. 30°- 80 lb 30° 160 lb 50° 60 ft Fig. P2.19 Fig. P2.20 25° 45° F F 180 ft. 8 tons Fig. P2.21 10 tons 8 tons 35° 20° x