Pressure is defined as the force applied per unit area. It is calculated by dividing the normal force (F) by the area (A) it is applied to, written as P=F/A. The SI unit for pressure is the pascal (Pa), which equals 1 newton per square meter. Pressure increases if the applied force increases or the area decreases. For example, a needle applies more pressure than a finger of equal force because the needle has a smaller contact area.

1. Understanding Pressure
1. Pressure on an area, A is the normal force, F, whish is being applied perpendicularly to the
area.
2. Pressure on an area, A is expressed as the normal force, F per unit area, A.
3. P = (F/A)
4. This SI unit for pressure is the pascal, Pa, where 1 Pa = 1 N/m2 (metre square).
5. Pressure is increased:
if the force, F applied to a given area, A is increased.
if a given force, F is applied to a smaller area, A.
6. If a balloon is pressed against by a finger, the balloon will only change its shape a bit. If the
balloon is pushed against by a needle with the same force, the balloon will burst. This is
because a finger has a larger surface area (A) than a needle. Hence, the needle exerts much
pressure than the finger and perforates through the surface of the balloon and making a hole
and freeing the air inside the balloon.
Definition of pressure:
Pressure is defined as force per unit area
Pressure=force/area
(P=F/A)
When force is in newtons(N) and area is in m2
, then pressure P is in N / m2
or pascal (Pa).
The following numerical example compares the pressure exerted on the floor by a girl of
weight 400N, when she wears a pair of shoes with high heels(having small area of contact
with floor) and when she wears a pair of slippers with large area of contact with floor.
With high heels
Force=400N
Area of heels=100X10-6
m2
(assumed)
Pressure=400/100X10-6
=4X106
N/m2
or Pa
With slippers.

2. Force=400N
Area of slippers=3000X10-6
m2
Pressure=400/3000X10-6
=0.13X106
N/m2
or Pa
Area of slippers is 30 times greater than area of heels. So pressure is 30 times greater in case
of heels.