For a cylindrical rod $($cross$-$section is a circle$)$ subjected to a uniaxial tensile load $P$ as

shown, given $P=500($lbs$),$ the length of the rod $L=15($inches$),$ and the diameter of the

cross$-$section of the rod D$=0\mathrm{.}5($inch$),$ what is the tensile stress developed within the cross$-$

section? If the rod elongation $=0\mathrm{.}012($inch$)$ under the load, what is the Young's Modulus

of the material?