Question $3(0\mathrm{.}4$ points$)$

$[$E$]$

Suppose a state of pure shear stress occurs $($say on a circular shaft under pure

torsion$).$ How many single$-$element strain gage should be employed to determine the

principal stresses ${}_{-}1$ and ${}_{-}2.$

$3$

$2$

$4$

$1$