Pressure is defined as force per unit area. The SI unit of pressure is the Pascal. Atmospheric pressure is the pressure exerted by the air layers surrounding Earth and can be measured using a barometer. Liquids exert pressure in all directions, with pressure increasing at greater depths. A manometer is used to measure liquid pressure.

2. words meaning
Pressure
The force acting per unit area of
the surface.
Pascal SI unit of pressure.
Thrust
Total force acting vertically on
the surface of a body.
Fluid The substance which can flow.
Manometer
A simple device used to measure
liquid pressure.
Atmospheric pressure
The pressure exerted by the
layer of air around the earth
barometer
The apparatus used for
measuring the air pressure

3.  Effect of force on a given area is called pressure.
 Pressure depends on two factors. They are: force
applied and area over which force acts.
 The formula of pressure is: Pressure=Force/Area.
 Pressure can also be defined in terms of another
force called thrust.
 The force acting on a body perpendicular to its
surface is called thrust.
 So, we can also define pressure as thrust per unit
area is Pressure=Thrust/Area.
 The SI unit of pressure is Pascal (Pa).

4.  It is easier to cut an apple from the sharper side
than blunt because the sharper side has less
area.
 Porters wear turbans while carrying heavy loads
on heads. By doing this pressure on their heads
gets reduced due to the increase in area of
contact.
 Wooden sleepers are kept below the railway
lines so that there is less pressure of the train on
the ground and railway lines do not sink into
the ground.

5.  Unlike solids, the liquids do not have a definite
shape. They take the shape of the containing vessels.
 The pressure in liquids is not thrust per unit area.
instead it depends it depends upon the depth and
density of the liquid.
 Fluids have weight so they exert pressure on the base
and walls of the container.
 The pressure at a depth in a liquid depends upon
two factors:
1) The height of the liquid column.
2) The density of the liquid.

6.  A manometer is a simple device used to
measure liquid pressure.
 It has a U – shaped tube which is fixed to a
wooden board having a scale.
 The U – tube is filled with coloured water
such that its limbs are half filled.
 One end of the U – tube is open, the other
end is fixed to a rubber tube which in turn
is connected to a thistle funnel .
 This improvised apparatus is called as
manometer .

7.  The pressure exerted by water in the oceans
increases with depth.
 When deep sea fishes are brought up to the
surface of the sea, their body flow at a Very high
pressure.

8.  Like all gases, air also have weight hence
exerts pressure.
 The force exerted by the atmosphere on
unit area is called atmospheric pressure.
 Air exerts huge pressure in every
direction.

9.  A barometer is an instrument used to
measure atmospheric pressure.
 It consists of long and thin tube filled
with mercury and closed at one end.
 The open end of the tube is placed in a
small trough full of mercury.
 The pressure exerted by air on the
mercury of trough is able to hold
certain height of the mercury column.
 When the air pressure is low, the
mercury will move down.
 When the air pressure increases, the
height of the mercury column increases

10.  The edge of the knife is made sharper increase
pressure.
 The sole of sport shoes have spikes have spikes
to increase the grip through pressure.
 In vacuum cleaner a low pressure is created
inside with the help of a fan and this low
pressure helps in the working of vacuum
cleaner.
 The straw helps us to drink juice because the
atmospheric pressure is exerted on the surface of
the juice.

11.  The pointed end of a high heeled shoe exerts
more pressure than what an elephant’s flat
exerts.
 It is due to the upward force exerted by water
that we are able to swim.
 The pressure of water vapours in a streaming
pressure cooker, cooks the food faster.
 The first mercury barometer was made by an
Italian scientist terriceilliinm 1643.
 submarines are built of hard thick sheets of
metal to withstand the high pressure of water.

12.  The effect of force on a given area is called
pressure.
 The SI unit of pressure is Pascal(Pa)equal to 1
Newton per meter square the pressure exerted
by air is called atmospheric pressure.
 Atmospheric pressure is measured with
barometer.
 A liquid exerts pressure in all direction.
 At the same depth the pressure is same in all
direction.
 Liquid pressure increases with depth.
 Liquid pressure is measured with manometer.