Page 123 - Science Class 08

Aim : To measure the pressure of a liquid at different levels.
Method:
Take a bucket filled with water. Slowly lower the funnel into the water.
As you go deeper and deeper into the water, the difference in the liquid
level goes on increasing. If you double the depth difference in liquid
pressure will also be doubled.

It shows that the pressure of a liquid increases with depth, but at the
same depth the pressure is the same in all direc ons.

ATMOSPHERIC PRESSURE pressure. It is equal to the force exerted by a

You know that our earth is surrounded by a mass of 1 kg on every square cen meter.
thin layer of air called atmosphere. The Now, you can imagine how much pressure is
atmosphere put a pressure on all the things exerted by air on us. But, why do we not feel
present on the earth. it? It is because, the equal amount of force

The weight exerted by the ver cal column of all acts upon our body from the opposite
layers of air of atmosphere on unit area of direc on. The two forces balance each other.
earth's surface is called the atmospheric Atmospheric air exerts a large pressure on an
object from all the direc ons.

Aim : To show the existence of atmospheric pressure.
Method:

Take a glass tumbler and fill it with water. Now, place a cardboard on
the tumbler. Press it on the mouth of the tumbler so that there is no
air le inside the tumbler. Hold the tumbler in the hand and invert it
upside down.
You will no ce that the cardboard do not fall even if we release it
free. The reason is that water exerts pressure on the upper surface of cardboard in downward
direc on and the atmospheric air exerts pressure on bo om surface of the cardboard in the
upward direc on. The pressure of atmospheric air is much larger than pressure of enclosed water.
So, the cardboard does not fall directly. Let us understand it with the help of another ac vity.

Aim : To show that atmosphere exert a large pressure in all direc ons.
Method:

Take a small container of n having a narrow mouth. This empty container is under pressure
from the air outside as well as inside. The air pressure inside of the container is equal to the
pressure outside of the container.

Science-8 123