$($a$)$ State the advantages in representing stresses using the Mohr's circle.

$($b$)$ An axial force P $($Figure $1($a$))$ and a torsional load T $($Figure I$($b$))$ both produce state of stresses shown.

$($i$)$ Draw the Mohr's circle for these cases

$($ii$)$ State in each case the principal stresses. the maximum in$-$plane shear stress average stress.

$($iii$)$Draw the element showing the orientation in which the maximum stresses and shear stresses occur.

FICURE. $1$

$($a$)$

$($b$)$