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AVMED > Physics of the Atmosphere > Flashcards

Physics of the Atmosphere Flashcards

1
Q

What does the atmosphere contain?

A

Mixture of:

  • Gases
  • Water Vapour
  • Suspended Particles
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2
Q

What forces act on the constituents that make up the atmopshere?

A
  • Expansion of gases as a result of solar heating

- For of gravity holding these constituents in place

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3
Q

What are the functions of the atmosphere?

A
  • Providing oxygen for animal respiration
  • Providing CO2 for plant respiration
  • Protection against ultra-violet and cosmic radiation
  • Propagation of sound waves
  • Source of rainwater contributing to water cycle.
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4
Q

What effect maintains the surface temperature of the earth?

A

Greenhouse effect

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5
Q

What are the layers of the atmosphere and what are their altitudes?

A

1) Troposphere ( 0 to 26,000 ft/58,000 ft depending on poles or at equator)
2) Stratosphere (Tropopause to 158,000 ft)
3) Mesosphere (158,000 ft –> 290, 000 ft)
4) Thermosphere (290,000 ft –> 700,000 ft)
5) Exosphere ( > 700,000 ft)

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6
Q

What occurs with the weather, temperature and pressure in the troposphere?

A
  1. Most weather phenomena occurs in the troposphere
  2. Temperature decreases at an ISA of -1.98/1000 feet until -56.6 degrees.
  3. Atmospheric pressure decreases with altitude.
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7
Q

What occurs with temperature in the stratosphere and what causes this?

A
  • Temp remains constant in lower levels, then increases to SL values in upper layers.
  • Occurs due to the reaction of UV radiation to create the ozone layer which releases heat.
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8
Q

What is characteristic of the mesosphere?

A

Rapid decline in temperature to about -113 C at an altitude of 290,000 feet.

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9
Q

What causes heating in the thermosphere and why is there no atmospheric temperature effect?

A
  • Heating is caused by the radiant energy from the sun, with temperatures rising as high as 1500 C.
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10
Q

What is the exosphere regarded as? What type of heating occurs in the exosphere?

A
  • The beginning of true space, where atmospheric gas gradually blends with interplanetary dust and gases.
  • Heating is from the radiant energy from the sun.
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11
Q

What is the volumetric composition of the atmospheric gases up to an altitude of 300,000 feet?

A

Nitrogen (N2) = 78.1%
Oxygen (O2) = 20.9%
Carbon Dioxide (CO2) = 0.03%
Other gases = 0.97%

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12
Q

What is the cause of decompression sickness (DCS) when the body is subjected to decreased atmospheric pressure?

A

Evolution of Nitrogen out of bodily fluids.

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13
Q

What occurs if too little O2 is given?

A

Impair the function of the brain and body cells.

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14
Q

What occurs if there is too much O2?

A

O2 toxicity can result.

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15
Q

What is CO2s role in the atmosphere and the human body?

A
  • Contributes to the greenhouse effect.

- In the human body, CO2 is a by-product and is crucial for control of respiration.

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16
Q

What is the water vapor pressure at 37 C? what is it at 100 degrees?

A
  • 47 mm Hg

- 760 mm Hg (1 atmosphere) at 100 C.

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17
Q

What is pressure, what is its symbol and what is the SI unit?

A
  • Pressure is force per unit area in a direction perpendicular to the surface of an object.
  • SI unit is the Pascal (Pa)
  • N.m^2
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18
Q

What is atmospheric pressure?

A

The combined weight of all the gases in the atmosphere.

19
Q

What is ISA, and what is its purpose?

A
  • ISA is international standard atmosphere.

- It is required as a yardstick to measure all relevant deviations off of.

20
Q

What are the assumptions of the ISA?

A
  • Air is dry and has a composition as in Table 1-1
  • Mean sea level pressure is 1013.25 hPa
  • Gravity = 9.8m/sec
  • Temperature at mean sea level is 15 C
  • Lapse rate is 1.98/1000 feet up to 36,089 feet.
  • Tropopause = 36,000 feet.
  • Isothermal layer of -56.5 C up to 65, 616 feet
  • Temp gradually increases above 65,616 feet
21
Q

What is atmospheric pressure at 18,000 feet?

A

1/2 atm

22
Q

What is atmospheric pressure at 25,000 feet?

A

1/3 atm

23
Q

What is atmospheric pressure at 48,000 feet?

A

1/8 atm

24
Q

What are the three physiological zones and what are their altitudes?

A
  1. Physiological Zone (MSL to 10,000 feet)
  2. Physiologically Deficient Zone (10,000 to 50,000 feet)
  3. Space Equivalent Zone (above 50,000 feet)
25
Q

What is the typical response of humans in the Physiological Zone?

A

Normal human physiological can compensate for the effects of altitude.

26
Q

What is the typical response of humans in the Physiologically Deficient Zone and what are the names of some problems?

A
  • Compensatory mechanisms can no longer cope with increasing altitude to maintain normally physiology.
  • Some problems include hypoxia, decompression illness and cold.
27
Q

What is time of useful consciousness at 18,000 feet?

A

20-30 minutes

28
Q

What is time of useful consciousness at > 45,000 feet?

A

9 to 12 seconds

29
Q

What is Armstrong’s line and what is the name of the condition that would occur in the human body at this altitude?

A
  • At 63,000 feet, atmospheric pressure is 47 mm Hg, this pressure equals the water vapour pressure of body fluids at 37 C which will cause them to boil spontaneously without the addition of heat.
  • Ebullism
30
Q

What is Charles’ Law and equation?

A

The volume of a gas varies directly with the temperature at a constant pressure. P1/P2 = T1/T2

31
Q

What is Amontons Gas Law and equation?

A

The pressure of a gas varies directly with the temperature at a constant volume. V1/V2 = T1/T2

32
Q

What is the law of gaseous diffusion?

A

Gas molecules will diffuse through a permeable membrane from an area of high pressure to one of low pressure.

33
Q

What is Boyle’s law, what is the equation and what effects does it result in in the body?

A
  • Volume of a gas is inversely proportional to the pressure, temperature remaining constant.
  • P1/P2 = V2/V1
  • It explains the effects of pressure change on gases trapped in body cavities such as in the ears, sinuses, gastro-intentional tract, lungs and teeth.
34
Q

What is Henry’s Law and what is the equation?

A
  • At a constant temperature, the amount of gas dissolved in a solution is directly proportional to the partial pressure that gas over the solution.
  • P1/P2 = A1/A2 where A = amount of dissolved gas.
35
Q

What is Dalton’s Law and what is the equation?

A

Pt = P1 + P2 + P3 + P4 + … + Pn

36
Q

What is Pascal’s Law?

A
  • Pressure applied to an incompressible fluid will be transmitted equally throughout the liquid.
  • Principle explains why pressure changes are transmitted throughout the body and affect even closed cavities deep within the body.
37
Q

What are the two types of cosmic radiation?

A
  • Galactic radiation

- Solar radiation

38
Q

Where does solar radiation originate from?

A

The sun

39
Q

What is secondary radiation?

A

As cosmic radiation particles enter the atmosphere, they collide with atmospheric molecules and give off secondary radiation.

40
Q

What is the predominant form of radiation at flight altitudes, and reaches a maximum at 70,000 feet?

A

Secondary radiation.

41
Q

What is hte unit for measuring radiation?

A

The Sievert (Sv).

42
Q

What determins the dose of radiation experienced by aircrew?

A
  • Altitude (atmospheric shielding and secondary radiation)
  • Latitude (magnetic shielding)
  • Solar flare activity (intentsity of solar flux)
43
Q

When are crew most at risk for radiation exposure?

A

Long haul, high altitude, trans-polar flights.

AVMED (1 decks)

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