A metal bar is shown above with a width of $"$b$"$ into the page and the modulus of Elasticity $"$E$."$

$L=250cm,h=2\mathrm{.}5cm,b=5cm,E=70$GPa,$F=200N$

a$.$ What is the maximum principal stress in the bar? Show equation and numerical value. $(2pt$

b$.$ The direction of force is reversed so that it is in the negative $x$ direction, as shown below. What

additional failure criteria should be considered to determine if the bar could withstand the

loading? $(2$ pt$)$