Pressure

• Pressure is the force per unit area: $\Pr essure\ \left(Pa\right)\ =$$\ \frac{Force\ \left(N\right)}{Area\ \left(m^2\right)}$ or $P\ =$$\ \frac{F}{A}$
• The unit of pressure is Pascals: $Pa\ =$$\ \frac{N}{m^2}$
• In liquids: $\Pr essure\ \left(Pa\right)\ =$$\ Density\ \left(\frac{kg}{m^3}\right)\ x\ Gravity\ \left(\frac{m}{s^2}\right)\ x\ Height\ \left(m\right)$
• As the depth of a fluid increases, the pressure caused by the whole liquid increases.
• The manometer:

  1. Measures the pressure difference between a liquid and the atmosphere
  2. The height difference shows the excess pressure in addition to the atmospheric pressure

  
• Barometer:

  • Tube with vacuum at the top and mercury filling the rest
  • Pressure of the air pushes down on reservoir, forcing mercury up the tube
  • Measure height of the mercury
  • ~760mm of mercury is 1 atm