Notesale: Turn your study into money

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Pressure – The Entire Topic

Pressure
This booklet has information, examples and questions on pressure for you to practise with
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Write down the numbers then write down the equation and
show your working
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As we live on the planet Earth, g is
equal to 9
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The unit for pressure is Pascal’s (Pa), named after one of these two:

If the force is 600N and the area is 4
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If the pressure is 600 Pa and the area is 3
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If the force is 150N and the pressure is 2
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Pressure – The Entire Topic
Solid Pressure
As solids cannot be compressed we can use the equation F = pA to show the following:

Force (N)

Area _____

600N

0
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25

Can you think of any other examples of small area = big pressure and big area = small pressure
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This can be seen in the “Tower
of Power” experiment which you hopefully saw last year
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From which
hole will the juice squirt out fastest and furthest? Can you explain why?
The lower the hole is the further the water squirts out
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This is the equation which we use
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There are three holes in it; 0
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25 and 0
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What is the pressure at these depths?
Method
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5 = 49
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459m
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The density of orange juice is 1
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8 m/s2
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495 x 1
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8 = 5
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You do the next two in the space below
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It has a height of 40 cm and a cross sectional
area of 0
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The maximum force it can withstand is 8
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If it is filled up with a liquid of density
6
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Will the bottle break and the liquid go all over the students toes? What are the two
equations that you need?
Question
Can you explain using the ideas of pressure why your ears hurt when you swim underwater? Put in a
few calculations to justify your answers
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0 kg/m3
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You will have felt air pressure when you are in a plane and your ears ‘pop’
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The Magdeburg hemispheres are joined
together and are easily separated until the air inside is removed whereupon it is much more difficult
as you have to act against the air pressure
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A lack of oxygen leads to oxygen deprivation and can
result in death
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Can you explain why crisp packets like this do this when on an aeroplane?

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Pressure – The Entire Topic
Question
The density of air is about 0
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Using the graph on the previous page, what is the difference
between the pressure at an altitude of 25 km compared to 1 km?
Method:
This is the equation which we use
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Difference in pressure = (25000-1000) x 0
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Now you have a try at these
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If the area of an aeroplane
window is 40 m2, what is the force exerted on the window? Can you explain why aeroplane windows
are always smaller than this?

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Pressure – The Entire Topic
Upthrust and Flotation
(Or why heavy object like a boat can float)


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bing
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What decides whether things sink or float?
Which of the following will sink?

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When an object is lowered into water the water level rises
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The more of the object in the water, the more water is displaced
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The
upward force is bigger than the downward force and this resultant force is the upthrust
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An object will sink when the upthrust is less than the weight
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Pressure – The Entire Topic

Example question
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Draw the force diagram to show the relative sizes of
the weight and the upthrust
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What can you say about the relative
sizes of the weights now?
Can you research and explain why ships have a plimsoll line?
Can you explain why the Titanic floated around quite happily until it started taking in water
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A sinks down to the bottom of the bowl, B floats
with half of it above the water and C floats with less than half above the water
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What can you say about their density compared to water?
An object is attached to a Newton-meter and it reads 5
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It is then put into water
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What conclusion can you draw concerning its density relative to that of
water?

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