This document discusses the concept of pressure in physics. It defines pressure as the force applied over an area, and provides an example comparing the pressure exerted by a fingertip versus a palm. Pressure is measured in units of pascals or other derivatives of newtons per area. The document explains that applying the same force over a larger area results in lower pressure. It provides examples of how high and low pressure are used in different situations like shoes on muddy ground, skis on snow, and knives cutting food. Finally, it briefly discusses how pressure increases with depth in liquids and can be transmitted through a liquid.

1. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20051 of 37
IGCSE Physics
Pressure

2. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20052 of 37
Pressure
Contents
Pressure in liquids
Pressure

3. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20053 of 37
Pressure is exerted whenever a force is applied over an area.
If the same force is applied in each picture, which arm exerts
the highest pressure on the board?
1. 2.
What is pressure?

4. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20054 of 37
The arm applies a force
to the board via a fingertip.
The force acts over a
small area and so
produces a high pressure.
1.
High and low pressure
The same force is now acting
over a larger area – the palm
has a greater surface area
than the fingertip.
A lower pressure is produced.
2.

5. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20055 of 37
Pressure is measured in:
Newtons per square metre (N/m2
), which are also called
pascals (Pa).
Pressure can also be measured in:
Newtons per square millimetre (N/mm2
);
Newtons per square centimetre (N/cm2
).
pressure =
area
force
P x A
F
Pressure is the force per unit area
and is calculated using this formula:
Calculating pressure

6. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20056 of 37
The same force spread over a larger area means a lower
pressure.
Which type of pressure?
Which type of shoes would be best for walking over a muddy
field – flat soles or heels?

7. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20057 of 37
The boots have flat soles
and spread the person’s
weight over a large surface
area.
These boots exert a low
pressure on the ground.
Which type of pressure?
In contrast, the heeled
shoes have a smaller
surface area and so
exert a higher pressure.
These shoes are likely
to sink into soft ground.

8. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20058 of 37
A force spread over a large area means low pressure,
e.g. skis and snowboards.
The large surface area
of the board means the
skier exerts very little
pressure on the snow.
This means he slides
over the top of the snow
and does not sink into it.
Using low pressure

9. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20059 of 37
A force concentrated on a small area means high pressure,
e.g. high heeled shoes, needles, ice skates, sharp knives.
The narrow blade of a knife
means that it exerts a high
pressure and makes it easier
to cut fruit and vegetables.
The high pressure of the
blade of an ice-skate melts
the ice and helps the skater
slide across the surface.
Using high pressure

10. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200510 of 37
Pressure
Contents
Pressure in liquids
Pressure
Summary activities

11. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200511 of 37
Pressure in a liquid:
 acts in all directions;
 increases with depth.
Pressure in a liquid
A liquid can be used to transmit
pressure from one place to
another.

12. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200512 of 37
high pressure
low pressure
The relationship between pressure and depth is shown
by a water bottle with holes along its length.
Pressure in a liquid