4.2.2. Newton’s Laws of Viscosity

Try these first

1. 1.

   Define shear stress.

   Hint

   Think about forces acting on surfaces.

2. 2.

   What is viscosity?

   Hint

   Consider how thick or thin a fluid is.

3. 3.

   What is the correct equation for Newton's law of viscosity?

   • τ = μ (du/dy)
   • τ = μ (dy/du)
   • τ = du/dy / μ

   Hint

   Consider what relation stresses have with velocity in fluids.

4. 4.

   True or False: Non-Newtonian fluids exhibit constant viscosity.

   • True
   • False

   Hint

   Recall the examples of fluids we discussed.

5. 5.

   If the dynamic viscosity of a given fluid is 0.015 Pa.s and the velocity gradient is 3 s^-1, what is the shear stress?

   Hint

   Keep the equation for shear stress in mind.

6. 6.

   Describe the flow behavior of a non-Newtonian fluid under varying shear rates and provide an example.

   Hint

   Think about common kitchen items for examples.