Recall from the study of elasticity (Chapter 50) that when a body is placed under transverse (shear) stress σ=Ft/A, the resulting strain ε is the tangential displacement \(...Recall from the study of elasticity (Chapter 50) that when a body is placed under transverse (shear) stress σ=Ft/A, the resulting strain ε is the tangential displacement x divided by the transverse distance l : Fluid flow undergoes a similar kind of shear stress; however, with fluids, we find that the stress is not proportional to the strain, but to the rate of change of strain:
