8.2.2. Atmospheric Pressure as a Datum

Try these first

1. 1.

   What happens to shear stress in a fluid at rest?

   Hint

   Think about forces acting on fluids that are not moving.

2. 2.

   Define gauge pressure.

   Hint

   Consider how we measure pressure relative to the surrounding atmosphere.

3. 3.

   What is gauge pressure?

   • A measure of pressure below atmospheric pressure
   • A measure of pressure above atmospheric pressure
   • Equal to absolute pressure

   Hint

   Think about how we define pressure on a gauge.

4. 4.

   True or False: Atmospheric pressure is constant at all altitudes.

   • True
   • False

   Hint

   Consider what happens when you climb mountains.

5. 5.

   Calculate the gauge pressure at a depth of 5 meters in a lake where water density is 1000 kg/m³. Assume atmospheric pressure is 101.3 kPa.

   Hint

   Use the hydrostatic pressure equation and subtract atmospheric pressure.

6. 6.

   Discuss how the capillary rise would change if the diameter of the tube is reduced to half while keeping the liquid and substrate material the same.

   Hint

   Think about the relationship between tube diameter and height of liquid rise.