Recall from the study of elasticity (Chapter 50) that when a body is placed under transverse (shear) stress \(\sigma=F_{t} / A\), the resulting strain \(\varepsilon\) is the tangential displacement \(...Recall from the study of elasticity (Chapter 50) that when a body is placed under transverse (shear) stress \(\sigma=F_{t} / A\), the resulting strain \(\varepsilon\) 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:
