Question $3(10$ Points$)$

Find the principal plane?

Do NOT use the Mohr circle for

Questions $3$ and $4.$

Question $4(10$ Points$)$

Determine the principal stress

on the princlpal plane found in

Question $3?$

Use the plane stress

transformation

equations given in

Question $2.$

${}_y=10$MPa

${}_x=15$MPa

${}_{xy}=5$MPa