Draw a small element with ${}_{}=+10$ksi,${}_{yy}=-2$ksi, and ${}_{xy}=+4$ksi. $($Note: this is still mechanics

convention, so you should draw the shear going UP on the right face and TO THE RIGHT on the

upper face$).$ Do the following: a$)$ Draw Mohr's circle. b$)$ Find the radius, which is also ${}_{xy}^{\text{M}\text{A}\text{X}},$ or

the maximum in$-$plane shear stress. c$)$ Find the principal stresses and show them on a properly

oriented element.

Answers: Principal stresses are $11\mathrm{.}21$ and $-3\mathrm{.}211$ ksi, max in$-$plane shear is $7\mathrm{.}21$ ksi, your element

should have a face $16\mathrm{.}84$ degrees ccw from the vertical with the principal stress of $11\mathrm{.}21($the

other is on the face perpendicular to that$).$