Atmospheric Pressure

2.2  Atmospheric Pressure
  Atmospheric pressure  

Pressure due to the weight of the layer of air acting on the surface of the Earth.


Instruments to measure atmospheric pressure

  • Fortin barometer
  • Mercury barometer
  • Aneroid barometer

Applications of atmospheric pressure

  1. Drinking straw
    • When straw is sucked, the air velocity in straw is high
    • The air pressure in the straw is lower than atmospheric pressure
    • Air is pushed up into a straw by atmospheric pressure
  2. Rubber sucker
    • When the rubber is pressed, the air is removed
    • There is low pressure inside rubber sucker (partial vacuum)
    • Atmospheric pressure is higher than pressure inside rubber
    • Rubber sucker sticks on surface
  3. Siphon
    • Atmospheric pressure is higher than the pressure in the siphone
    • The atmospheric pressure acting on liquid push the liquid down to a lower container
  4. Syringes
    • When the piston is pulled, the pressure in the syringe decreases
    • The pressure in the syringe is lower than atmospheric pressure
    • The atmospheric pressure at the surface force water into the syringe.
  5. Vacuum cleaner
    • Vacuum fan removes air from space inside dust bag
    • The pressure in the dust bag is lower than atmospheric pressure
    • Outside air is sucked into the dust bag together with dusts