The truss ABC shown in the figure supports a horizontal load P1 = 300 lb and a vertical load P2 = 900 lb. Both bars have cross-sectional area A = 2.4 in.2 and are made of steel with E = 30 × 106 psi.
(a) Determine the strain energy U1 of the truss when the load P1 acts alone (P2 = 0).
(b) Determine the strain energy U2 when the load P2 acts alone (P1 = 0).
(c) Determine the strain energy U3 when both loads act simultaneously.

30 B P, 300 lb P2 900 lb 60 in