A rigid bar of weight W = 750 lb hangs from three equally spaced wires, two of steel and one of aluminum (see figure). The diameter of the wires is 1/8 in. Before they were loaded, all three wires had the same length.
What temperature increase ΔT in all three wires will result in the entire load being carried by the steel wires? (Assume Es = 30 × 106 psi, αs = 6.5 × 106 / °F, and αa = 12 × 106 / °F.)