- On the surface of the earth, there is a thick layer of gas called the atmosphere. The atmosphere consists of various types of gas called the atmospheric gas.
- The atmospheric gases collide on the surface of the earth and hence exert a pressure on the surface of the earth, called the atmospheric pressure.
- The atmospheric pressure can be measured in the unit of atm, mmHg or Pa. The atmospheric pressure at sea level is taken to be 1 atm, which is approximately 760 mmHg or 101,000 Pa.
Characteristics of Atmospherics Pressure
- Decreases with altitude
The atmospheric pressure changes accordingly to the altitude. Altitude is the height above sea level. The greater the altitude, the lower the atmospheric pressure.
- Act equally in all direction
The atmospheric pressure acts on every object in the atmosphere. It acts equally in all direction.
- Atmospheric pressure is ~ 100,000Pa at sea level
On the surface of the earth, the atmospheric pressure can be as high as 101,000 Pa.
Unit Used to Measure Atmospheric Pressure
- The following are the unit used to measure atmospheric pressure
- Pascal (Pa)
1 Pa = 1 N/m²
- Standard Atmospheric Pressure (atm)
1 atm = Atmospheric Pressure at sea level ( = 101,325 Pa)
- mmHg (also known as torr)
1 mmHg = 1/760 atm (roughly equal to the liquid pressure exerted by a millimetre of mercury).
- milibar (Not used in SPM)
- In SPM, usually we use the unit cmHg, instead of mmHg.