Question

The bar DA is rigid and is originally held in the horizontal position when the weight W is supported from C. The wires are made of A-36 steel and have a cross-sectional area of 0.002 in^2determine the weight W.

Answer 1

Answer:

W = 112 lb

Explanation:

Given:

- δb = 0.025 in

- E = 29000 ksi      (A-36)

- Area A_de = 0.002 in^2

Find:

Compute Weight W attached at C

Solution:

- Use proportion to determine δd:

                              δd/5 = δb/3

                              δd = (5/3) * 0.025

                              δd = 0.0417 in

- Compute εde i.e strain in DE:

                               εde = δd / Lde

                               εde = 0.0417 / 3*12

                               εde = 0.00116

- Compute stress in DE, σde:

                               σde = E*εde

                               σde = 29000*0.00116

                               σde = 33.56 ksi

- Compute the Force F_de:

                               F_de = σde *A_de

                               F_de = 33.56*0.002

                               F_de = 0.0672 kips

- Equilibrium conditions apply:

                               (M)_a = 0

                               3*W - 5*F_de = 0

                               W = (5/3)*F_de

                              W = (5/3)* 0.0672 = 112 lb