3. 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.
4. 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. If the force is concentrated on a small area, the
force is creating a high pressure
If the force is spread over
a large area, the pressure
will be less
6.
7. Sharks have sharp teeth.
When they bite, the force
creates high pressure to
crush their prey
High pressure
9. Sharp knife is better at cutting
Because it will be concentrated
on a small area to create high
pressure
10. Low pressure
Camels have wide feet.
Their weight is spread over a
large area.
The pressure will be low and so,
they will not sink into the sand
11. Snowshoes is wide and does
not sink into the snow.
The force is spread over a
large area so, it creates low
pressure
12. Explain the following in your answers,
Use the words ‘pressure’, ‘force’ and ‘area’
a) A truck used in the desert has wide tyres.
b) A drawing pin has a sharp point at one end and a large, flat head at the other.
15. Pressure is measured in:
Newtons per metre square (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
16. A force of 8N pressing on an area of 4m².
Calculate the pressure
17. A hammer hits a nail with a force of 200N.
The point of the nail has an area of 0.5mm² touching a
piece of wood.
Calculate the pressure on the wood
18. A rectangular block weighs 240N.
The area of the block in contact with the floor is 20cm².
Calculate the pressure on the floor.
23. The same force spread over a larger area means a lower
pressure.
Which type of shoes would be best for walking over a muddy field – flat
soles or heels?
24. 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.
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.
25. P A
F
A footbridge has been designed to withstand a pressure of
2000Pa.
The area of the bridge is 15m².
What is the greatest force the bridge can withstand?
26. P A
F
When the wind blows, it creates pressure on any surface it blows
against.
A large window has an area of 3.5m².
If the wind causes a pressure of 2000Pa on the window, what force
acts on it?
28. Divers have to be careful if they
want to dive to a great depth in
the sea.
The weight of the water above presses
down on them.
The greater the depth, the more water
presses down
So, the pressure is greater
The bar is a metric unit of pressure, but is not approved as part of the International System of Units (SI). It is defined as
exactly equal to 100,000 Pa
29.
30. Pressure in a liquid:
acts in all directions;
increases with depth.
31.
32. If you climb a high mountain,
The air gets thinner ( less dense )
So, the pressure is less
We call the pressure of air atmospheric
pressure
Atmospheric pressure is greatest at sea
level
Because the weight of the whole
atmosphere is above us, pressing down.
33. What happens to the pressure of a gas if more gas is
squashed into a container?
34. What happens to the pressure of a gas if it is squashed into a
smaller volume?
