4.3.1. Molecular Levels and Viscosity

Try these first

1. 1.

   Define shear stress in the context of fluid dynamics.

   Hint

   Think of friction between two moving fluid layers.

2. 2.

   What happens to liquid viscosity when the temperature is increased?

   Hint

   Consider how heating affects movement at a molecular level.

3. 3.

   What is shear stress?

   • Force per unit area acting perpendicular to fluid layers
   • Force per unit area acting parallel to fluid layers
   • Density of the fluid

   Hint

   Relate it to friction between fluids.

4. 4.

   True or False: Increasing temperature decreases the viscosity of gases.

   • True
   • False

   Hint

   Think about how molecules interact at higher temperatures.

5. 5.

   A bacterial culture medium has a viscosity of 0.9 Pa.s at 25°C. If the temperature increases to 37°C, how will the viscosity change? Assume it behaves like a typical liquid.

   Hint

   Consider the behavior of liquids as they heat up.

6. 6.

   You have a fluid that behaves as a dilatant; as shear stress increases, the required force to maintain flow also increases. Describe an application where this property might be beneficial.

   Hint

   Think about scenarios where increasing resistance to flow could provide safety.