I A copper wire of diameter 2 mm is 10 m long and stretched out between two posts. The normal stress(pressure), a= E(L-LONL, depends on the length,L, versus the unstretched length, La, and Young's modulus, E = 1.1 x 106 kPa. The force is F=da and is measured to be 110 N. How much longer is the wire, and how much work was put in?

Fig: 1