Answer to Question #345886 in Physics for seph

Question

IV. An iron wire 1.0 m long with a square cross-section 2.0 mm on a side is used  

              to support a 100 kg load. Find the change in length. 

Answer 1

$$\sigma=\varepsilon E$$ $$\frac{F}{A}=\frac{\Delta l}{l_0}E$$ $$\Delta l=\frac{Fl_0}{AE}=\frac{mgl_0}{AE}$$ $$\Delta l=\frac{100*9.8*1.0}{4.0*10^{-6}*200*10^9}\\ =1.23*10^{-3}\:\rm m=1.23\: mm$$