8.1- Physics of the Atmosphere

Question 1

What is air?

Answer 1

The mixed air that makes up the atmosphere.

Question 2

What does the air comprimise?

Answer 2

21% oxygen
78% nitrogen
1% other gasses

Question 3

What are the “other” gasses in our air?

Answer 3

Argon, carbon dioxide and more.

Question 4

What happens to the composition of air as altitude increases?

Answer 4

It stays relatively the same, however pressure decreases.

Question 5

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

Answer 5

Its mass contribution.

Question 6

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

Answer 6

0.2

Question 7

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

Answer 7

60,000 feet

Question 8

What is the average height of the atmosphere?

Answer 8

760km

Question 9

What does the exosphere extend to?

Answer 9

10,000km

Question 10

What 5 parts is the atmosphere divided into?

Answer 10

Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
(TSMTE)

Question 11

What is the densest layer of the atmosphere?

Answer 11

Troposphere

Question 12

How far does the Troposphere extend?

Answer 12

8-14.5 km

Question 13

What aircraft fly in the troposphere?

Answer 13

Light aircraft and turboprops

Question 14

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

Answer 14

Vertical air movement

Question 15

What is the tropopause?

Answer 15

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

Question 16

Where does the tropopause lie above the equator?

Answer 16

Approx 17km

Question 17

Why do jet airliners generally cruise in the tropopause?

Answer 17

Air is thinner resulting in less drag.

Question 18

What is the tropopause also known as?

Answer 18

The isothermal layer because the temp is constant.

Question 19

What height does the stratosphere extend too?

Answer 19

50km

Question 20

What does the stratosphere include?

Answer 20

Ozone layer

Question 21

In the stratosphere does the temp vary?

Answer 21

No

Question 22

What temp is the stratosphere?

Answer 22

-56.5c

Question 23

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

Answer 23

Pressure
Temperature
Density
Humidity

Question 24

What is relative humidity referred too as?

Answer 24

Dimensionless ratio

Question 25

What is a pascal equal too?

Answer 25

N/m squared

Question 26

What does the ICAO deem the pressure at sea level?

Answer 26

1013 hPa (14.7psi)

Question 27

What is the second method of calculation for static pressure?

Answer 27

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

Question 28

What do barometers measure?

Answer 28

Absolute pressure

Question 29

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

Answer 29

Aneroid capsules

Question 30

What is temperature a measure of?

Answer 30

Average kinetic energy of molecules.

Question 31

What is the absolute zero degrees c in kelvin?

Answer 31

273.15

Question 32

In aviation what is actual atmospheric temperature expressed as?

Answer 32

Outside Air Temperature

Question 33

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

Answer 33

-56.5 degrees c

Question 34

What is the equation for density?

Answer 34

p=m/v

Question 35

As altitude increases, pressure and density.....?

Answer 35

Decrease

Question 36

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

Answer 36

Directly proportional too each other and inversely proportional to height.

Question 37

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

Answer 37

Temperature

Question 38

What makes air density vary?

Answer 38

Relative humidity and temp

Question 39

What is relative humidity?

Answer 39

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

Question 40

What is the relative humidity at 40,000ft?

Answer 40

1 or 2%

Question 41

Density decreases as humidity....?

Answer 41

Increases

Question 42

Humidity is greatly affected by...?

Answer 42

Temp

Question 43

Pressure, temp and humidity all affect...?

Answer 43

Air density

Question 44

Where does dynamic pressure act?

Answer 44

Direction of airflow.

Question 45

What is dynamic pressure denoted by?

Answer 45

q

Question 46

How is dynamic pressure worked out?

Answer 46

half p x v squared p is fluid density

Question 47

What is 1 bar equal too?

Answer 47

100,000 pascals

Question 48

What is the standard atmosphere by ICAO known as?

Answer 48

International standard atmosphere (ISA)

Question 49

What is the ISA sea level value of pressure?

Answer 49

1013.25 hPa

Question 50

What is the ISA sea level value of density?

Answer 50

1.225kg/m3

Question 51

What is the ISA sea level value of temp?

Answer 51

288.15K or 15 degrees c

Question 52

What is the standard altitude for tropopause?

Answer 52

11km (36,000ft)

Question 53

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

Answer 53

6.5 degrees c per km.

Question 54

In the stratosphere does the temp stay relatively the same?

Answer 54

Yes

Question 55

What is speed?

Answer 55

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

Question 56

What is acceleration?

Answer 56

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

Question 57

What is work?

Answer 57

Done when an object is moved over a distance

Question 58

What is work denoted by?

Answer 58

Joule and measured in N/M

Question 59

What is the equation for power?

Answer 59

Work over time.

Question 60

What is the speed of sound denoted by?

Answer 60

a

Question 61

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

Answer 61

Approximation of the total of all the relevant constant values.

Question 62

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

Answer 62

kelvin

Question 63

Formula for speed of sound?

Answer 63

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

Question 64

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

Answer 64

Lower