5.5 Pressure and Pressure Differences in Fluids

• Fluid


  A liquid or a gas
• In any fluid, the forces due to pressure act on a given surface at right angles (normal to) the surface
• Calculating pressure


  Pressure = Force/Area
• Pressure


  Pascals (Force in Newtons, Area in metre²)
• As altitude increases


  The density of the atmosphere decreases
• Earth's atmosphere


  A thin (relative to the magnitude of the Earth) layer of gas surrounding the Earth
• Equation for pressure in liquids at different depths

  1. Pressure due to a column of liquid(Pa) = Column height(m) x density(kg/m³) x gravitational field strength(N/kg)

  2. P = hρg
• Upthrust


  The weight of the fluid that the object displaces
• Factors that influence whether an object will sink or float


  • Upthrust
  • Weight
  • Density of fluid