A steel bar AD (see figure) has a cross-sectional area of 0.40 in.2 and is loaded by forces P1 = 2700 lb, P2 = 1800 lb, and P3 = 1300 lb. The lengths of the segments of the bar are a = 60 in., b = 24 in., and c = 36 in.
(a) Assuming that the modulus of elasticity E = 30 × 106 psi, calculate the change in length δ of the bar. Does the bar elongate or shorten?
(b) By what amount P should the load P3 be increased so that the bar does not change in length when the three loads are applied?

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