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Liquid Pressure

Liquids exert pressure in all directions.

 


One of the most important properties of liquids is that they exert pressure in all directions.

Take a rubber ball and make a small hole in it.

Pour water into it until it is full.
 

Pierce the ball at different places with a sharp needle.

Hold the ball in your hand with the thumb closing the opening at the top.

Now press the ball.
 

You will find that water rushes through the needle holes with same speed. This proves that liquid exerts pressure in all direction.
 

Other important properties of liquids are

(i) Pressure increases with depth.

(ii) Pressure is the same at all points at the same depth.

(iii) Liquid seeks its own level.

Take a tall vessel.

Drill four small holes at different depths.

Close the holes with a strip of tape.

Fill the vessel with water to the brim.

Now remove the strip of tape.
 

You will find that water rushes out with the great force from the hole at the bottom, with less force from the hole at the centre and with least force from the hole at the top. This shows that pressure increases with depth.
 

Example

Did you know ?

Solution

You will find that water rushes out with the great force from the hole at the bottom, with less force from the hole at the centre and with least force from the hole at the top. This shows that pressure increases with depth.The concept of pressure increasing with depth is used while constructing the dams.The dams are constructed by making the walls usually larger at the bottom than at the top in order to help withstand the pressure.
 

 


 

Perform a similar experiment as in the above activity with holes made at the same height on the metal can. Observe what happens. You will find that water rushes out with equal force from all the holes. This proves that pressure is the same at all points at the same depth.

A Liquid Seeks its Own Level

 

One of the important properties of a liquid is that it always comes to rest in a container with its upper surface horizontal.

Pour water into any one limb of a several interconnecting vessels of different shapes as in fig. The water level stands at the same level in all the vessels irrespective of their shape and size. This shows that a liquid finds its own horizontal level.
 

Question

Did you know ?

Solution

A spirit level is a device used to find out whether a surface is horizontal or inclined.
Find out for yourself where and by whom it is frequently used.
 

 

 

Think…. When we drink very cold liquids, we usually use a straw. It is the atmospheric pressure acting on the surface of the liquid that causes it to rise up the straw when air is sucked up.

 


 

Question

How do fountains work ?

Solution

Fountains work due to the pressure exerted by water on the walls of the pipe.

 





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