Pressure
Pressure is defined as force acting per unit area. Its SI unit is Pascal or N/m^{2}. Its formula is Pressure: \(\frac{Thrust (F)}{Area (A)}\)
Thrust:
The force acting perpendicularly on a surface is called the thrust. It is a vector quantity. The SI unit is Newton (N).
One Pascal pressure:
One Pascal pressure is defined as the pressure exerted on a surface of area 1m^{2}by the thrust of 1N.
Pressure depends on following factors:
 Thrust
 area
Proof of P = \(\frac{F}{A}\)
Let 'F' be the force acting perpendicularly, 'A' be the area and 'P' be the pressure exerted.
Then,
Pressure is directly proportional to the force acting perpendicularly.
Or, P ∝F.............................(i)
Pressure is inversely proportional to the area on which force acts.
P∝\(\frac{1}{A}\) .............................. (ii)
Combining equation (i) and (ii), we get
P∝\(\frac{F}{A}\)
or, P=K\(\frac{F}{A}\) [ where K is a constant ]
If 'F' is 1N, 'A' is 1m^{2} and the pressure is 1N/m^{2}, then
K=1
so, P=\(\frac{F}{A}\)
 Pressure is defined as force acting per unit area. Its SI unit is Pascal or N/m^{2}. The formula Pressure is Pressure= \(\frac{Thrust (F)}{Area (A)}\)
 Force is an external agent that changes or tends to change the state of a body. It is a cause of pressure,It is measured in newton, dyne, etc.
 Pressure is the thrust on unit area of surface. It is the effect of force acting on unit area, measured in N/m^{2}.
A sharp knife has smaller area at its edge than a blunt knife. When a force is applied on the knife, The pressure exerted by the edge of sharp knife is more than the pressure exerted by the blunt knife during cutting. Due to this reason, cutting with a sharp knife is easier than cutting with blunt knife.
When the area is increased by keeping the magnitude of force constant, the pressure exerted is decreased because pressure is inversely proportional to the area of surface that receives the force.
When a man stands with one foot the area of surface where the force is applied is decreased and as a result the pressure is increased because keeping the force constant, the pressure is inversely proportional to the area of surface that receives the force.
 The pressure, the force applied is directly proportional to its magnitude, that receives the area.
P α F……….. (i)
 The force that gives pressure is inversely proportional to the area that receives the force.
P α ………….. (ii)
P α
P = K
If 1 N force is applied in 1 square meter area, then the pressure will be 1N/m^{2} and thus, k=1.
Mass of a man (m) = 60 kg
Acceleration due to gravity (g) = 10 m/s^{2}
Weight of the man (F) = 600 N
Area occupied by one foot (A) = 150 cm^{2} =0.015 m^{2}
Pressure exerted (P) =?
P =
=
=40,000 N/m^{2}
This pressure exerted by the man on the ground when he stepped with one foot is 40,000 Pa.
Here,
Mass of Anupama (m) = 30 kg
Weight of Anupama (f) = mg = 30 kg × 10 m/s^{2}= 300N
Surface area of a sandal (A) = 150 cm^{2} =0.015 m^{2}
Pressure exerted (P) =?
P =
=
=20,000 N/m^{2}
This pressure exerted by the sandal on ground when Anupama stands on one foot is 20,000 Pa.
The pressure is defined as “the force acting perpendicularly per unit area”. The pressure is defined as the perpendicularly applied force on a unit area. The SI unit of pressure is N/m^{2}. It is also called Pascal (pa).
Following are the examples show us the extensive use of pressure in our daily life:
 Food is cooked faster in a pressure cooker than an open pot due to high air pressure.
 Among the taps of same size and connected to a common pipeline in a house, the flow of water from the tap on the lower floor is more than on the higher floor.
The two factors that affect the pressure are as follows:
 The magnitude of force(f)
 The surface area on which force is extended.
The pressure developed in 1 meter area when 1N of force is applied is called 1 Pascal of pressure.
1 pa =Here, Area of the base (A) = 10 cm x 18 cm
= 0.1 m x 0.18 m
= 0.018\(m^{2}\)
Depth of water in the vessel (h) = 4 cm = 0.04 m
Density of water (d) =1000 kg/\(m^{3}\)
∴Force on the base (F) =?
We know that
P = dgh
= 1000 \(\times\) 10\(\times 0.04 = 400Nm^{2}\)
Again we that
\(P =\frac {F}{A}\)
∴ F =P ×A
= 400 × 0.018
=7.2N
Here, Mass of the girl (m) = 30 kg
Surface area of single shoe (A) = 100 cm^{2}
= 1 ×10^{4}m^{2}
∴ Weight(F) = mg
= 30 ×10 = 300N
We know that,
p=\(\frac{F}{A}\)
=\(\frac{300}{1 ×10^{4}}\)
= 3 ×10^{6}pa
Hence, pressure exerted on the ground is 3 × 10^{6}pa.

Force acting per unit area is ______.
friction
gravitation
mechanics
pressure

Pressure is a ______.
scaler
none
scaler and vector
vector

SI unit of pressure is ______.
N/m^{4}
N/m^{4}
N/m^{2}
N/m^{2}

With increase in altitude, the pressure of the atmosphere ______.
may increase or decrease
increase
neither increase nor decrease
decrease

Pressure is defined as ______.
mass × volume
force × distance
force/area
mass/volume

The pressure (P) exerted by the liquid is at ______.
bottom of vessel
side of vessel
above the vessel
side and bottom of the vessel

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