What is Atmosphere?

The atmosphere is the blanket of air that surrounds the Earth.
It extends hundreds of kilometers above us and is made up of gases like nitrogen, oxygen, carbon dioxide, etc.

What is Atmospheric Pressure?

The air in the atmosphere has weight, and because of this weight, it presses on everything around us.
This force exerted by air per unit area is called atmospheric pressure.

Even though we don’t feel it, atmospheric pressure is very strong because air is pressing from all sides.

🧪 Measurement Using a Barometer

Atmospheric pressure is measured using an instrument called a barometer.

  • A mercury barometer shows the height of mercury pushed up by air pressure.

  • Higher mercury column = higher air pressure.
    Barometers are used in weather forecasting because pressure changes indicate weather changes.

🌐 Air Exerts Pressure in All Directions

Air pushes:

  • Upward

  • Downward

  • Sideways

That’s why:

  • Our bodies don’t get crushed—because the pressure inside our body balances the outside pressure.

  • Suction-based tools work.

📌 Applications of Atmospheric Pressure

1. Suction Cups

When a suction cup is pressed on a surface:

  • Air inside the cup is pushed out

  • Pressure inside becomes low

  • Higher atmospheric pressure outside pushes the cup and makes it stick firmly.

2. Drinking with a Straw

When you suck air from a straw:

  • Air pressure inside the straw decreases

  • Atmospheric pressure on the liquid’s surface pushes the liquid up into the straw
    That is why liquids rise when you drink with a straw.

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