9.10.3 pressure
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Transcript of 9.10.3 pressure
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IGCSE Physics
Pressure
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Pressure
Contents
Pressure in liquids
Pressure
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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?
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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.
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Pressure is measured in:Newtons per square metre (N/m2), which are also calledpascals (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
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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?
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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.
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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
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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
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Pressure
Contents
Pressure in liquids
Pressure
Summary activities
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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.
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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
