Lesson 1.2c Definition of Viscosity

**Goals** You can:

- Explain the meaning of stress, shear stress, normal stress, rate-of-shear-strain, velocity gradient
- Explain the meaning of a Newtonian Fluid and a Non-Newtonian Fluid. Give examples of fluids in each of these categories.
- Relate shear stress and velocity gradient using the definition of viscosity (Eq. 1)

\begin{align} \tau =\mu \frac{dV}{dy} \end{align}

**Rationale**

- Shear stress (i.e. viscous stress) causes head loss, pressure drop, drag, energy loss etc. It is of paramount importance in many practical applications.

**Resouces**

- Text section 2.4
- Non-newtonian on wikipedia
- Shear thickening fluid on a speaker--youtube