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SAI International School
Class VII
Lesson Notes
Subject: Physics
Ch-Wind, Storm and Cyclones
Subtopic: Air Pressure
Air Pressure:
Earth is covered by blanket of air called as Atmosphere.
The pressure exerted by the weight of the air is called as Air pressure or Atmospheric pressure.
So, atmosphere exerts pressure on us from all directions.
Pressure is simply defined as force exerted in a unit area.
Mathematically,
P= ி
SI unit of pressure is Pascal.
Other units of pressure are bar, atm, torr, mm of Hg, etc.
Factors affecting Air pressure are:
I. Altitude
II. Temperature
III. Humidity
Altitude:
The air pressure decreases as we move upwards from the surface of the earth.
It is because the number of air molecules reduces at higher altitude.
Temperature:
