Pressure is defined as the force applied per unit area. The formula for pressure is P=F/A, where P is pressure, F is force, and A is area. Pressure is directly proportional to force and inversely proportional to area. The shorter the area over which a given force is applied, the greater the pressure will be. The SI unit for pressure is the pascal, which is equal to one newton per square meter. Examples of how pressure applies in daily life include a sharp knife cutting better due to greater pressure from its small surface area and porters decreasing pressure on their heads by increasing the area over which heavy loads are supported.

1. Grade 8
Physics
Topic: Force and pressure
~Dr Lalit Kishore,
Plenum School, HP, India
Concept of Pressure

2. Defining pressure
 Normal / perpendicular force (thrust) acting per
unit area is called ‘pressure’
Pressure = Force / Area
 If
P # Pressure (Read # as stands
for)
F # Force
A # Area
 Then
P = F / A

3. Formula reading

4. Interpreting pressure formula
p = F / A
Means P is directly proportional to
F for the same A
Means P is inversely proportional
to A for the same F
 The shorter the area on which a
given force acts, the more the
pressure

5. Formula reading

6. Unit of pressure
 SI unit of pressure is Pascal
 Pressure is said be one Pascal when a
force of one Newton acts on area of one
square metre
1 Pascal = 1 Newton / Square
metre
 In abbreviation, it is written as follows

7. Experiment with Nail and Thumb
Tack
 Take a wood piece and try pushing hard
with thumb the nail into it, you will find it
difficult to get the nail into the wood
 But if you try pushing the drawing pin
with thumb of the cap, the drawing pin
will get into wood block.
 Less force on cap of the drawing pin
becomes pressure on the lesser area of
the tip of the pin

8. Applications of pressure in daily
life
 A sharp knife with thin or small-area edge cuts
better since small area results into greater
pressure to pierce through the object.
 A porter increases the area for heavy load on the
head by putting thick rounded cloth on head and
hence decrease pressure on the head. It make
carrying heavy load easier and less hurtful.