A rigid bar of weight W = 800 N hangs from three equally spaced vertical wires (length L = 150 mm, spacing a = 50 mm): two of steel and one of aluminum. The wires also support a load P acting on the bar. The diameter of the steel wires is d_s = 2 mm, and the diameter of the aluminum wire is d_a = 4 mm. Assume E_s = 210 GPa and E_a = 70 GPa.

(a) What load P_allow can be supported at the midpoint of the bar (x = a) if the allowable stress in the steel wires is 220 MPa and in the aluminum wire is 80 MPa? (See figure part a.)

(b) What is Pillow if the load is positioned at x = a/2?

(c) Repeat part (b) if the second and third wires are switched as shown in the figure part b.

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L S A VP S Rigid bar of weight W