Which one of the relationships is correct is one of the principal stress is zero at a point in two-dimensional stress system and the normal stress on two mutually perpendicular planes are σx and σy (both like) and the shear stress is τxy?
1
\(\tau _{xy}^2 = {\sigma _x}{\sigma _{y}}\)
2
\({\tau _{xy}} = \sqrt[3]{{{\sigma _x}{\sigma _y}}}\)
3
\(\tau _{xy}^2 =2 {\sigma _x}{\sigma _{y}}\)
4
\({\tau _{xy}} = \frac{{{\sigma _x} + {\sigma _y}}}{{{\sigma _x} - {\sigma _y}}}\)