The last question on my homework (always the hardest). 1. The problem statement, all variables and given/known data A wire of diameter 1.0mm and length 2.3m is made of copper. Young modulus is 1.1 x 10^11. Find: a) The cross-section of the wire in m² b) The strain if the wire is stretched by 0.85mm c) The stress d) The force necessary to cause the stress 2. Relevant equations (Pie)r² strain = extension/original length stress = Force/area 3. The attempt at a solution Here is my attempt, I get stuck at C, but please check what I've done so far. A) if (pie)r² then stick that into the calculator, and I get 7.8 x 10 ^7 B) Extension/Original length= 0.85/2.3 = 0.37 c) Hmm, they ask for stress but there is no force given, so how do I work that out? d) Now they ask the force needed to cause the stress, but I need that to work out the stress. Very confusing Any help is greatly appreciated.