$[$Ans: ${}_{\text{l}\text{o}\text{n}\text{g}\text{i}\text{t}\text{u}\text{d}\text{i}\text{n}\text{a}\text{l}}=18\mathrm{.}3mm]$

$5.$ Draw a linear elastic stress$-$strain graph and explain the following material properties: $($a$)$ Young's modulus, $($b$)$ proportional limit$,($c$)$ modulus of resilience, and $($d$)$ modulus of toughness.