Page 1 - lesson note- atmospheric pressure

SAI INTERNATIONAL SCHOOL
Class8
Lesson Notes
Subject-Physics
CH-Force and Pressure
Subtopic-Atmospheric Pressure

v Atmospheric pressure: Pressure exerted by the air or atmosphere around us is
called atmospheric pressure.
v Cause of atmospheric pressure: It is caused due to weight of air
v Atmospheric pressure value at sea level: 101.3 Kilopascal, 760 mm of mercury
column, 1 atm, 1013 mbar
v Barometer is used to measure atmospheric pressure

Factors affecting atmospheric pressure
a. Altitude: As the altitude increases the density of air decreases and atmospheric
pressure decreases.
b. Temperature: As the temperature increases the atmospheric pressure
decreases.
c. Humidity: As the humidity increases the atmospheric pressure decreases.

Applications
a. Many instruments like rubber sucker are based on this principle.
b. We are able to drink from the straw because of atmospheric pressure.
c. Ink dropper is based on this principle.

Significance of atmospheric pressure in our daily life
a. Mountaineers suffer from nose bleeds at higher altitudes: As we go
higher the density of air decreases so the atmospheric pressure
decreases. The pressure inside our body becomes relatively more
compared to outside pressure, s our nose starts bleeding.
b. Our ear pops when in the flight: The pressure inside the cabin becomes
relatively less as compared to the pressure inside the body so our ear may
pop.

Measurement Tools for atmospheric pressure:
Manual Instruments: Mercury Barometer, Aneroid Barometer
Digital and Electronic Instruments: Digital Barometer, Barometric Altimeter, MEMS
Pressure Sensor, Smartphone Barometer
Remote Sensing Instruments: Satellite Remote Sensors, Weather Buoy, Automated
Weather Station