Understanding Atmospheric Pressure for Class 8

Atmospheric pressure plays an important role in our daily life, from weather changes to how we breathe and live on Earth. Even though we cannot see it, the air around us constantly presses on everything, including our bodies and surroundings. From flying airplanes to simple activities like drinking through a straw, atmospheric pressure quietly influences many real-life situations. In this article, we will study what is atmospheric pressure, its meaning, and how it is measured.

Table of Contents

• Did you know?
• What is Atmospheric Pressure?
• Barometer: An instrument that Measures Atmospheric Pressure

Did you know?

To demonstrate the strength of atmospheric pressure, a large copper ball was sealed at the rims with grease. The air was pumped out, with only a vacuum inside. Two teams of eight horses could not pull apart this pair of copper hemispheres. These hemispheres were called Magdeburg hemispheres.

What is Atmospheric Pressure?

Our Earth is surrounded by different layers of gases called the atmosphere.

The atmosphere extends to a height of 480 km above the surface of the Earth, though the density of the gases starts decreasing from 100km onwards. Due to the weight of these gases, the atmosphere exerts a pressure called atmospheric pressure (also called barometric pressure).

The value of atmospheric pressure is about 105 Pa on a unit surface area, which feels like the weight of a big elephant sitting on your head.

Barometer: An instrument that Measures Atmospheric Pressure

When we go above the Earth’s surface, due to the decrease in the density of the gases, the atmospheric pressure decreases with height. The device used to measure atmospheric pressure is called a barometer.

A barometer is a scientific instrument that measures atmospheric pressure, the weight of the atmosphere pressing down on Earth. It helps predict weather changes; rising pressure indicates fair weather, while falling pressure suggests storms or rain.

Now, think, if the atmospheric pressure is so high, then why are you not crushed under this tremendous pressure?

We are not crushed by atmospheric pressure because there is air inside our bodies that pushes outward.

This inside pressure balances the air pressure outside our body. Since both pressures are equal, they cancel each other out. That is the reason why, even though air pushes on us from all sides, we do not feel crushed.

Our bodies contain air and fluids that exert internal pressure. This internal pressure is almost equal to the atmospheric pressure acting on us from outside. Since both pressures are balanced, they cancel each other out, and we do not feel crushed.

So, even though atmospheric pressure is very high, the equal pressure inside and outside the body keeps us safe and stable.

So far, we have seen how atmospheric pressure exists all around us and how it changes with height. We also studied the instrument that is used to measure atmospheric pressure and why it is important in everyday life.