8.1 physics of the atmosphere Flashcards

1
Q

Gases and Liquids are known as

A

Fluids

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2
Q

what makes up our atmosphere

A

21 % oxygen
78 % nitrogen
1 % other gases

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3
Q

what happens to air as altitude increases

A

composition remains the same.
but the pressure in the gas decreases

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4
Q

the chemical composition of air starts to change when

A

at 60,000 ft

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5
Q

usually oxygen accounts for approximately 0.2 ATM. what happpens if the local pressure is halved

A

the partial oxygen pressure only accounts for 0.1 ATM and vice versa

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6
Q

compressibility allows air density to vary with what

A

pressure and temperature

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7
Q

what is the average height of the atmosphere

A

760km

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8
Q

exosphere extends to around

A

10,000km

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9
Q

the atmosphere is divided into 5 main regions what are they

A
  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
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10
Q

the troposphere starts where and extends how far

A

earth’s surface 8-14.5 km (5 - 9 miles)

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11
Q

what is the densest layer of the atmosphere

A

troposhere

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12
Q

where do most modern jet aircraft cruise and why

A

tropopause , because the air is thinner which means less drag and higher fuel efficiency. also above most of the weather reducing turbulence

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13
Q

the tropopause is how far from the equatorial and polar regions

A

17km and 9km

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14
Q

the tropopause is also known as what

A

isothermal layer

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15
Q

stratosphere starts where and extends how far

A

just above troposphere and extends 50km it also contains the protective Ozone layer

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16
Q

temp in the stratosphere is usually about

A

-56.5 c

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17
Q

aircraft flight is highly influenced by what

A

pressure (P)
temperature (T)
density (p)
humidity (“relative humidity”)

18
Q

formula for atmospheric Pressure is

A

P = F/A force / surface area

19
Q

the unit of pressure is pascal (Pa) which is equivalent to what

A

newton of force per metre squared area

N/m2

20
Q

static pressure =

A

P = p x g x h atmos density x gravitational field strength x height of atmos

21
Q

barometers measure what

A

absolute pressure

22
Q

what is used on aircraft to measure absolute pressure

A

aneroid capsules

23
Q

SI unit for temperature is

A

degrees celsius

24
Q

as altitude increases.. pressure and density

24
the actual atmospheric temperature is very often expressed as what
outside air temperature (OAT)
24
equation for density is
p = m/V density = mass/unit volume
25
relative humidity is expressed as a
% percentage
26
as humidity increases, the air density...
decreases
27
what affects air density
pressure, temperature and humidity
28
humidity is greatly affected by what
temperature
29
dynamic pressure acts only in which direction
direction of the airflow
30
dynamic pressure is denoted by what letter
q and is often called "q pressure"
31
ISA is what
international standard atmosphere
32
the isa values at sea level are
pressure 1013.25hPa density 1.225 kg/m3 temperature 288.15 k or 15 degrees c
33
air temperature decreases with increased altitude at a linear rate within the troposphere
.
34
work =
force x distance N x m measured in newton metres
35
acceleration =
change of speed/ time taken for change V2 - V1 / time
36
power =
work/ time or. force x distance/time
37
is the speed of sound higher or lower at high altitudes
lower because the temperature is lower
38
A barometer measures what
Absolute pressure
39
What is the standard altitude for the tropopause
36,000 ft (11 km)