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CAT B- Mod 8 Aerodynamics > 8.1- Physics of the Atmosphere > Flashcards

8.1- Physics of the Atmosphere Flashcards

1
Q

What is air?

A

The mixed air that makes up the atmosphere.

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2
Q

What does the air comprimise?

A

21% oxygen
78% nitrogen
1% other gasses

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3
Q

What are the “other” gasses in our air?

A

Argon, carbon dioxide and more.

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4
Q

What happens to the composition of air as altitude increases?

A

It stays relatively the same, however pressure decreases.

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5
Q

What is the pressure level of each part of the mixture is proportional to? (air)

A

Its mass contribution.

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6
Q

If the local pressure is 1 atmosphere (1 ATM) then how many atmospheres of oxygen are there?

A

0.2

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7
Q

At what altitude does the composition of air start to change?

A

60,000 feet

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8
Q

What is the average height of the atmosphere?

A

760km

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9
Q

What does the exosphere extend to?

A

10,000km

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10
Q

What 5 parts is the atmosphere divided into?

A

Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
(TSMTE)

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11
Q

What is the densest layer of the atmosphere?

A

Troposphere

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12
Q

How far does the Troposphere extend?

A

8-14.5 km

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13
Q

What aircraft fly in the troposphere?

A

Light aircraft and turboprops

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14
Q

What occurs in the troposphere as a consequence of solar heating?

A

Vertical air movement

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15
Q

What is the tropopause?

A

Thermodynamic gradient-stratification layer that marks the end of the troposphere.

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16
Q

Where does the tropopause lie above the equator?

A

Approx 17km

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17
Q

Why do jet airliners generally cruise in the tropopause?

A

Air is thinner resulting in less drag.

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18
Q

What is the tropopause also known as?

A

The isothermal layer because the temp is constant.

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19
Q

What height does the stratosphere extend too?

A

50km

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20
Q

What does the stratosphere include?

A

Ozone layer

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21
Q

In the stratosphere does the temp vary?

A

No

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22
Q

What temp is the stratosphere?

A

-56.5c

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23
Q

What are they key factors of the atmosphere that effect aircraft flight?

A

Pressure
Temperature
Density
Humidity

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24
Q

What is relative humidity referred too as?

A

Dimensionless ratio

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25
Q

What is a pascal equal too?

A

N/m squared

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26
Q

What does the ICAO deem the pressure at sea level?

A

1013 hPa (14.7psi)

27
Q

What is the second method of calculation for static pressure?

A

pxgxh
p= atmospheric density
g= gravitational field strength
h= height of the atmosphere

28
Q

What do barometers measure?

A

Absolute pressure

29
Q

Barometers are not practical on aircraft so what is used instead?

A

Aneroid capsules

30
Q

What is temperature a measure of?

A

Average kinetic energy of molecules.

31
Q

What is the absolute zero degrees c in kelvin?

A

273.15

32
Q

In aviation what is actual atmospheric temperature expressed as?

A

Outside Air Temperature

33
Q

At 36,000ft what does the air temp stabilise at?

A

-56.5 degrees c

34
Q

What is the equation for density?

A

p=m/v

35
Q

As altitude increases, pressure and density…..?

A

Decrease

36
Q

What are density and pressure directly proportional too and inversely proportional too?

A

Directly proportional too each other and inversely proportional to height.

37
Q

Assuming fluids are allowed to expand freely, density decreases as what increases?

A

Temperature

38
Q

What makes air density vary?

A

Relative humidity and temp

39
Q

What is relative humidity?

A

Amount of water vapour present in the air compared to the max amount of water vapour the air can hold.

40
Q

What is the relative humidity at 40,000ft?

A

1 or 2%

41
Q

Density decreases as humidity….?

A

Increases

42
Q

Humidity is greatly affected by…?

A

Temp

43
Q

Pressure, temp and humidity all affect…?

A

Air density

44
Q

Where does dynamic pressure act?

A

Direction of airflow.

45
Q

What is dynamic pressure denoted by?

A

q

46
Q

How is dynamic pressure worked out?

A

half p x v squared
p is fluid density

47
Q

What is 1 bar equal too?

A

100,000 pascals

48
Q

What is the standard atmosphere by ICAO known as?

A

International standard atmosphere (ISA)

49
Q

What is the ISA sea level value of pressure?

A

1013.25 hPa

50
Q

What is the ISA sea level value of density?

A

1.225kg/m3

51
Q

What is the ISA sea level value of temp?

A

288.15K or 15 degrees c

52
Q

What is the standard altitude for tropopause?

A

11km (36,000ft)

53
Q

How much does the temp decrease per km in the troposphere?

A

6.5 degrees c per km.

54
Q

In the stratosphere does the temp stay relatively the same?

A

Yes

55
Q

What is speed?

A

Distance that a moving object covers in a unit of time.

56
Q

What is acceleration?

A

The change in speed divided by the time during which the change takes place.

57
Q

What is work?

A

Done when an object is moved over a distance

58
Q

What is work denoted by?

A

Joule and measured in N/M

59
Q

What is the equation for power?

A

Work over time.

60
Q

What is the speed of sound denoted by?

A

a

61
Q

In the formula for speed of sound what is the number 20?

A

Approximation of the total of all the relevant constant values.

62
Q

In the formula for speed of sound what is the temperature always expressed in?

A

kelvin

63
Q

Formula for speed of sound?

A

a= 20 x (square root of) T(m/s)

64
Q

If the temperature is lower what happens to the speed of sound?

A

Lower

CAT B- Mod 8 Aerodynamics (4 decks)

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