고체역학 (Gere) — Axially Loaded Members: Problem 2.7-4

2.7-4 The bar \(ABC\) shown in the figure is loaded by a force \(P\) acting at end \(C\) and by a force \(Q\) acting at the midpoint \(B\). The bar has a constant axial rigidity \(EA\). (a) Determine the strain energy \(U_1\) of the bar when the force \(P\) acts alone (\(Q = 0\)). (b) Determine the strain energy \(U_2\) when the force \(Q\) acts alone (\(P = 0\)). (c) Determine the strain energy \(U_3\) when the forces \(P\) and \(Q\) act simultaneously upon the bar.