8.1 physics of the atmosphere Flashcards
Gases and Liquids are known as
Fluids
what makes up our atmosphere
21 % oxygen
78 % nitrogen
1 % other gases
what happens to air as altitude increases
composition remains the same.
but the pressure in the gas decreases
the chemical composition of air starts to change when
at 60,000 ft
usually oxygen accounts for approximately 0.2 ATM. what happpens if the local pressure is halved
the partial oxygen pressure only accounts for 0.1 ATM and vice versa
compressibility allows air density to vary with what
pressure and temperature
what is the average height of the atmosphere
760km
exosphere extends to around
10,000km
the atmosphere is divided into 5 main regions what are they
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
the troposphere starts where and extends how far
earth’s surface 8-14.5 km (5 - 9 miles)
what is the densest layer of the atmosphere
troposhere
where do most modern jet aircraft cruise and why
tropopause , because the air is thinner which means less drag and higher fuel efficiency. also above most of the weather reducing turbulence
the tropopause is how far from the equatorial and polar regions
17km and 9km
the tropopause is also known as what
isothermal layer
stratosphere starts where and extends how far
just above troposphere and extends 50km it also contains the protective Ozone layer
temp in the stratosphere is usually about
-56.5 c
aircraft flight is highly influenced by what
pressure (P)
temperature (T)
density (p)
humidity (“relative humidity”)
formula for atmospheric Pressure is
P = F/A force / surface area
the unit of pressure is pascal (Pa) which is equivalent to what
newton of force per metre squared area
N/m2
static pressure =
P = p x g x h atmos density x gravitational field strength x height of atmos
barometers measure what
absolute pressure
what is used on aircraft to measure absolute pressure
aneroid capsules
SI unit for temperature is
degrees celsius
as altitude increases.. pressure and density
decrease
the actual atmospheric temperature is very often expressed as what
outside air temperature (OAT)
equation for density is
p = m/V density = mass/unit volume
relative humidity is expressed as a
% percentage
as humidity increases, the air density…
decreases
what affects air density
pressure, temperature and humidity
humidity is greatly affected by what
temperature
dynamic pressure acts only in which direction
direction of the airflow
dynamic pressure is denoted by what letter
q and is often called “q pressure”
ISA is what
international standard atmosphere
the isa values at sea level are
pressure 1013.25hPa
density 1.225 kg/m3
temperature 288.15 k or 15 degrees c
air temperature decreases with increased altitude at a linear rate within the troposphere
.
work =
force x distance N x m measured in newton metres
acceleration =
change of speed/ time taken for change
V2 - V1 / time
power =
work/ time or. force x distance/time
is the speed of sound higher or lower at high altitudes
lower because the temperature is lower
A barometer measures what
Absolute pressure
What is the standard altitude for the tropopause
36,000 ft (11 km)
