Pressure Flashcards

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1
Q

what is pressure?

A

The force per unit area

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2
Q

how do you calculate pressure?

A

Area (m2)

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3
Q

what is pressure measured in?

A

newtons per square metre (N/m2) or pascals (Pa)

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4
Q

what does weight spread over a small area produce?

A

high pressure

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5
Q

what does weight spread over a large area produce?

A

low pressure

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6
Q

what does pressure in liquids depend on?

A

depth - the greater the depth, the greater the pressure

and the density of the liquid

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7
Q

how does pressure act?

A

equally in all directions

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8
Q

does air have weight?

A

yes

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9
Q

does air have mass?

A

yes

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10
Q

does air occupy space?

A

yes

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11
Q

give an example of an experiment you could do to show that air has weight

A

put an inflated balloon on a balance

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12
Q

give an example of an experiment you could do to show that air takes up space

A

put a glass in a basin a quarter filled with water with a plastic tube running into it. blow water into it and the water level rises on the outside

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13
Q

what is atmospheric pressure due to the weight of air presing down on the earth

A

the weight of air pressing down on the earth

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14
Q

what happens to atmospheric pressure as we increase our height above sea level?
why?

A

it decreases

the weight of air decreases

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15
Q

what is used to measure atmospheric pressure?

A

a barometer

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16
Q

what weather does high atmospheric pressure bring?

A

good, settled weather

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17
Q

what weather does low atmospheric pressure bring?

A

bad, unsettled weather

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18
Q

give three everyday applications of pressure

A

Hydraulics forces liquids from one size space to another size e.g. car brakes
Water supply system: The higher a reservoir above a house, the greater the water pressure in the house.
Medicine:Blood pressure is an indication of how healthy a person is

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19
Q

what does the effect of a force on a surface depend on?

A

how it is spread out over the surface

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20
Q

give an example of weight spread over a small area and it’s effects

A

The woman with the stiletto heels can cause damage to floor covering
as her weight is concentrated over a small area.

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21
Q

give an example of pressure in water

A

When underwater, a diver experiences pressure from the liquid all around him. The deeper he dives, the greater is the pressure exerted

22
Q

does with or shape affect pressure?

A

no

23
Q

is the pressure in a liquid equally or unequally distributed?

A

equally

24
Q

is air a fluid?

A

yes

25
Q

how does air exert pressure?

A

in the same way as liquids

26
Q

do the experiment to show that air exerts pressure

A

.

27
Q

does the atmosphere exert pressure?

A

yes

28
Q

do the experiment to show that air has mass

A

.

29
Q

does air have volume?

A

yes

30
Q

do the experiment to show that air has volume

A

.

31
Q

give two examples of atmospheric pressure

A

rubber suckers

a card on a glass jar of water

32
Q

name a type of barometer

A

a mercury barometer

ananeroid barometer

33
Q

describe how a mercury barometer works

A

atmospheric pressure holds up the column of mercury

34
Q

what does normal atmospheric pressure hold up?

A

Normal atmospheric pressure holds up a column of 76 cm of mercury.

35
Q

what happens in a mercury barometer when atmspheric pressure increases?

A

When atmospheric pressure increases, the mercury rises slightly up the tube.

36
Q

what happens in a mercury barometer when atmspheric pressure decreases?

A

When atmospheric pressure decreases, the mercury falls slightly down the tube.

37
Q

what is special about the aneroid barometer?

A

it uses no liquid

38
Q

what is an aneroid barometer made of?

A

a partially evacuated corrugated box

39
Q

what happens to the aneroid barometer if the atmospheric pressure increases?

A

If atmospheric pressure increases, the box is crushed slightly, causing the pointer to move.

40
Q

what happens to the aneroid barometer if the atmospheric pressure decreases?

A

When the pressure decreases, the pointer moves the other way

41
Q

what is the instrument used by pilots to measure height above sea level and how is it used?

A

When we move higher above sea level:
The atmospheric pressure decreases.
An instrument called an altimeter is used by pilots to measure height above sea level.
It does this by measuring the pressure on a barometer.

42
Q

what happens in the weather when the atmospheric pressure is high?

A

When the atmospheric pressure is high:
Water vapour does not rise from the ground.
This means that rain clouds do not form and
the weather is fine and sunny

43
Q

what happens to water vapour when the atmospheric pressure is high?

A

it does not rise from the ground

44
Q

what happens in the weather when the atmospheric pressure is low?

A

When the atmospheric pressure is low:
Water vapour rises up from the ground.
Rain clouds form, which may cause rain

45
Q

what happens to water vapour when the atmospheric pressure is low?

A

When the atmospheric pressure is low:

Water vapour rises up from the ground

46
Q

give the three points on high pressure

A

high pressure
heavy air (sinking)
happy weather

47
Q

give the three points on low pressure

A

Low pressure
Light air (rising)
Lousy weather

48
Q

what do the lines on a weather chart show?

A

The lines on a weather chart show areas of equal pressure.

49
Q

What shows areas of equal pressure on a weather chart?

A

isobars

50
Q

what are the lines on a weather chart called?

A

isobars

51
Q

what are isobars shown as on weather charts?

A

Isobars are shown on weather charts as areas of high pressure and low pressure.