Atmospheric pressure

• Atmospheric pressure is defined as the pressure exerted on an object by the weight of the air above it. The Atmospheric pressure on the Earth’s surface at sea level is about one hundred thousand pascal, i.e., 100 kPa.
• Atmospheric pressure is measured using an instrument called barometer.
• We know that there is air all around us. This envelop of air is called as the atmosphere.

• The weight of air in a column of the height of the atmosphere and area 10 cm x 10 cm is as large as 1000 kg. The reason we are not crushed under this weight is that the pressure inside our bodies is also equal to the atmospheric pressure and cancels the pressure from outside.

Variation of Atmospheric pressure with altitude:

• The altitude of a place is its height above sea level.
• Atmospheric pressure decreases with the increase in altitude.
• If the pressure of atmosphere is changed suddenly, the blood vessels on our body will burst due to pressure. This is why astronauts have to wear special pressurized suits.