Sometimes cos phi cos lambda in Equation 7.2 is termed the Schmid factor. Determine the magnitude of the Schmid factor for an FCC single crystal oriented with its [120] direction parallel to the loading axis. A single crystal of zinc is oriented for a tensile test such that its slip plane normal makes an angle of 65 degree with the tensile axis. Three possible slip directions make angles of 30 degree, 48 degree, and 78 degree with the same tensile axis. Which of these three slip directions is most favored? If plastic deformation begins at a tensile stress of2.5 MPa (355 psi), determine the critical resolved shear stress for zinc.