Question

a truss is made by hinging two uniform, 150-N rafters as shown in Fig. 5-21. They rest on an essentially frictionless floor and are held together by a tie rope. A 500-N load is held at their apex. Find the tension in the tie rope.

Answer 1

Let L and R be the left and right vertical floor reactions
let T be the tension of the rope
 summation of all forces is zero

R + L - 500 - 150- 150 = 0

R + L = 800

 since the triangle formed is isosceles triangles, the legs are equal
R = L = 400 N

using the summation of the torque

  L [ 4] - T[ 3 - (2 *3/5)] = 0
400 [ 4] - T[ 1.8] = 0
T = 1600/1.8
T = 889 N