Simple tension and compression tests on a brittle material reveal that failure occurs by...

Simple tension and compression tests on a brittle material reveal that failure occurs by fracture at MPa and MPa, respectively. In an actual application, the material is subjected to perpendicular tensile and compressive stresses, respectively, such that Determine the limiting values of and according to (a) the Mohr theory for an ultimate stress in torsion of MPa and (b) the Coulomb–Mohr theory. [Hint: For case (a), the circle representing the given loading is drawn by a trial-and-error procedure.]