A shop sign weighing 215N is supported by a uniform 130N beam of length L = 1.67m.
1. The guy wire is connected D = 1.20m from the backboard. Find the tension in the guy wire. Assume theta = 42.4o
2. Find the horizontal force exerted by the hinge on the beam.
3. Find the vertical force exerted by the hinge on the beam. Use "up" as the positive direction.
T = tension in the wire
L = length of beam
Mg = weight of sign = 215 N
mg = weight of beam = 130 N
using equilibrium of torque about A
T Sin42.4 (D) = mg (L/2) + MgL
T Sin42.4 (1.20) = (130) (1.67/2) + (215) (1.67)
T = 577.88 N
2,
using equilibrium of forces along the horizontal direction
Fx = horizontal force exerted by the hinge on the beam = T Cos42.4 = 577.88 Cos42.4 = 426.74 N
3.
using equilibrium of forces along the vertical direction
Fy = vertical force exerted by the hinge on the beam
using equilibrium of forces in vertical direction
Fy + T sin42.4 = mg + Mg
Fy + 577.88 Sin42.4 = 130 + 215
Fy = - 44.7
negative sign suggest Fy is in down direction
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