An elliptical bar with lateral surface defined by $x_2^2+2x_3^2=1$ has the following stress

distribution:

$=\left[\begin{array}{ccc}0& -2x_3& x_2\\ -2x_3& 0& 0\\ x_2& 0& 0\end{array}\right]$

$($a$)$ Show that the stress vector at any point $(x_1,x_2,x_3)$ on the lateral surface is zero.

$($b$)$ Find the resultant force, and resultant moment, about the origin $O,$ of the stress vector on the

left end face $x_1=0.($Note: the resultant moment is given by $\{$:$M_o={\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}x$TdA$).$