Atmospheric Pressure and Altitude Effects
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Questions and Answers

What happens to atmospheric pressure as altitude increases?

  • It fluctuates unpredictably.
  • It decreases. (correct)
  • It increases steadily.
  • It remains constant.

How is atmospheric pressure typically measured?

  • In inches of mercury. (correct)
  • In kilograms per meter squared.
  • In pounds per square inch.
  • In millibars.

What is absolute pressure?

  • The pressure at sea level.
  • The average air pressure on Earth.
  • The sum of atmospheric pressure and gauge pressure. (correct)
  • The pressure exerted by a liquid only.

What is gauge pressure?

<p>The pressure measured relative to atmospheric pressure. (D)</p> Signup and view all the answers

What is the approximate decrease in atmospheric pressure with every 1,000 feet of altitude increase?

<p>1 inch of mercury. (C)</p> Signup and view all the answers

What is the formula for calculating absolute pressure?

<p>Gauge Pressure + Atmospheric Pressure (B)</p> Signup and view all the answers

What does gauge pressure represent?

<p>Pressure relative to ambient pressure (A)</p> Signup and view all the answers

How does atmospheric air density change with altitude?

<p>It decreases with higher altitude. (D)</p> Signup and view all the answers

What is the density of air at sea level?

<p>1.225 kg/m³ (D)</p> Signup and view all the answers

What occurs when air is compressed?

<p>Air density increases. (D)</p> Signup and view all the answers

What best describes density in relation to a substance?

<p>Property unique to each substance (B)</p> Signup and view all the answers

What happens to air density when moving from low altitude to high altitude?

<p>It decreases significantly. (B)</p> Signup and view all the answers

Which of the following statements about atmospheric pressure is true?

<p>It is required to calculate absolute pressure. (A)</p> Signup and view all the answers

What happens to temperature as altitude increases in the troposphere?

<p>Temperature decreases as altitude increases. (A)</p> Signup and view all the answers

What is the unit of measurement for atmospheric pressure at sea level?

<p>Pounds per square inch (A)</p> Signup and view all the answers

How does atmospheric pressure change with altitude?

<p>It decreases with altitude. (B)</p> Signup and view all the answers

What factors can affect the actual pressure at a given location and time?

<p>Altitude, temperature, and density of the air (C)</p> Signup and view all the answers

At sea level, what force does the atmosphere exert per square inch?

<p>14.7 pounds (B)</p> Signup and view all the answers

What effect does altitude have on aircraft performance?

<p>Affects take-off, rate of climb, and landings (C)</p> Signup and view all the answers

Which statement about atmospheric pressure is accurate?

<p>It is a measure of force exerted on a given area. (A)</p> Signup and view all the answers

What can be inferred about the relationship between air density and altitude?

<p>Air density decreases with altitude. (C)</p> Signup and view all the answers

What condition makes air the lightest or least dense?

<p>When it contains the maximum amount of water vapour (C)</p> Signup and view all the answers

What is the total mass of 5 water molecules and 5 oxygen molecules given their atomic masses?

<p>250u (C)</p> Signup and view all the answers

How is density calculated based on mass and volume?

<p>Density = Mass/Volume (C)</p> Signup and view all the answers

What is the density of air at 250u total mass in a volume of 1m³?

<p>250u/m³ (B)</p> Signup and view all the answers

Which of the following statements about atmospheric conditions is true?

<p>Atmospheric conditions vary continually, even hourly. (D)</p> Signup and view all the answers

What is the purpose of the International Standard Atmosphere (ISA)?

<p>To base all aerodynamics calculations on a consistent model (A)</p> Signup and view all the answers

What significant observation is related to the ISA?

<p>It is derived from data taken at 45 degrees latitude north and south. (C)</p> Signup and view all the answers

What factor does NOT affect air density at a particular altitude?

<p>Volume of air (A)</p> Signup and view all the answers

What does humidity measure?

<p>The amount of water vapor in the atmosphere (D)</p> Signup and view all the answers

Which of the following describes relative humidity?

<p>The actual amount of moisture in the air relative to the maximum it can hold (A)</p> Signup and view all the answers

What factor primarily influences the level of humidity in the air?

<p>The temperature of the air (B)</p> Signup and view all the answers

Which expression of humidity indicates the total moisture a specific volume of air can hold?

<p>Absolute humidity (A)</p> Signup and view all the answers

In what type of environment would you expect to find very low humidity levels?

<p>Deserts like the Atacama Desert (C)</p> Signup and view all the answers

How is humidity typically expressed?

<p>In percentage (B)</p> Signup and view all the answers

What is the dew point a measure of?

<p>The temperature at which air becomes saturated and water vapor condenses (B)</p> Signup and view all the answers

What does a relative humidity of 75% indicate about the moisture in the air?

<p>The air can still hold an additional 25% moisture. (A), The air is holding 75% of the maximum moisture it can hold. (C)</p> Signup and view all the answers

What happens to water vapor absorption in the air as the temperature increases?

<p>Water vapor absorption increases (D)</p> Signup and view all the answers

How does high humidity affect the sensation of sweating?

<p>Sweat is absorbed by the air, preventing any sweating sensation. (B), Sweat remains on the skin, causing discomfort. (C)</p> Signup and view all the answers

What is absolute humidity a measure of?

<p>The actual amount of water vapor in a specific volume of air. (C)</p> Signup and view all the answers

What defines the dew point in meteorological terms?

<p>The temperature at which air reaches full saturation and begins to condense. (A)</p> Signup and view all the answers

In regions with low humidity, how does it affect sweating?

<p>Sweat evaporates quickly, making people feel cooler. (C)</p> Signup and view all the answers

Which of the following correctly describes the relationship between temperature and moisture capacity in the air?

<p>Warmer air can hold more moisture than cooler air. (B)</p> Signup and view all the answers

What is represented by the term 'moisture capacity' in relation to air?

<p>The maximum amount of moisture air can hold at a specific temperature. (B)</p> Signup and view all the answers

How is absolute humidity measured?

<p>In milligrams of water vapor per liter of air. (A)</p> Signup and view all the answers

Flashcards

Atmospheric Pressure

The force exerted by the weight of air in the atmosphere on a surface.

Barometer

An instrument used to measure atmospheric pressure.

Altitude and Pressure

As altitude increases, atmospheric pressure decreases.

Gauge Pressure

The pressure measured relative to the surrounding atmosphere.

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Absolute Pressure

The total pressure measured from a vacuum.

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Troposphere Temperature

The temperature in the troposphere decreases as altitude increases. The air is warmest near the Earth's surface and cools with height.

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Sea Level Pressure

At sea level, the atmosphere exerts a pressure of 14.7 PSI. This means a 1-inch square column of air from the surface to the atmospheric limit weighs 14.7 pounds.

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Factors Affecting Pressure

Temperature, density, and altitude all influence atmospheric pressure. These conditions affect aircraft performance, especially take-off, climb, and landings.

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Absolute Pressure (PSIA)

The total pressure exerted by a fluid, including atmospheric pressure. It is the sum of gauge pressure and atmospheric pressure.

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Gauge Pressure (PSIG)

The pressure measured relative to atmospheric pressure. It is the difference between absolute pressure and atmospheric pressure.

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Density

A measure of how much mass is contained in a given volume. For air, it indicates how tightly packed the air molecules are.

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Air Compressibility

Air can be squeezed into a smaller volume. This means that the density of the air increases when compressed.

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Air Density and Altitude

Air density decreases as altitude increases. This is because there is less air pressing down at higher altitudes.

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Sea Level Air Density

Air density at sea level is approximately 1.225 kg/m3. This value is often used as a reference point.

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Air: Unique Property

Each substance has a unique density. It is a ratio of mass to volume.

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Relative Humidity

The percentage of moisture the air is holding compared to the maximum it can hold at a given temperature and pressure.

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High Humidity

When the air contains a large amount of moisture, close to its maximum capacity for that temperature.

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Low Humidity

When the air contains a small amount of moisture, far from its maximum capacity for that temperature.

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Absolute Humidity

The actual amount of water vapor present in a specific volume of air.

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Dew Point

The temperature at which air becomes saturated with moisture and condensation begins.

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Moisture Saturation

When air reaches its maximum capacity for holding moisture at a given temperature.

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Condensation

The process of water vapor in the air changing into liquid water, forming droplets.

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How does temperature affect humidity?

As temperature increases, air can hold more moisture. As temperature decreases, air can hold less moisture and may become saturated, leading to condensation.

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Air Density & Water Vapor

Air is least dense (lightest) when it contains the maximum amount of water vapor, which corresponds to 100% relative humidity.

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Air Density Formula

The density of air is calculated by dividing its mass by its volume (Density = Mass/Volume).

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Air Density Factors

Air density is influenced by factors like temperature, humidity, and altitude.

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International Standard Atmosphere (ISA)

A standard model of atmospheric conditions used for aviation and other applications, based on observations at 45° latitude.

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ISA Purpose

The ISA provides consistent reference conditions for calculating aerodynamic forces, performance, and other aircraft-related values.

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ISA & ICAO

Both International Standard Atmosphere (ISA) and International Civil Aviation Organization (ICAO) use the same standard atmosphere model.

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Non-uniformity of Air

Air pressure and density do not decrease uniformly with altitude, and atmospheric conditions vary greatly.

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Humidity

The amount of water vapor in the air or a gas.

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What affects humidity?

Temperature plays a major role in humidity. Higher temperatures allow more water vapor to be absorbed into the air.

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Dry Places

Locations with low humidity, often found in deserts or high altitudes.

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Humidity and Temperature Relationship

As temperature increases, the air's capacity to hold water vapor also increases. This means warmer air can hold more moisture than colder air.

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Study Notes

Introduction to Atmosphere

  • The atmosphere is derived from the Greek words "atmos" (vapor) and "sphaira" (sphere).
  • Earth's atmosphere is a layer of air surrounding the planet, extending approximately 500 miles (800 km).
  • The atmosphere comprises 4 concentric gaseous layers.

Atmospheric Composition

  • The atmosphere is primarily composed of:
    • 78% Nitrogen
    • 21% Oxygen
    • 0.9% Argon
    • 0.03% Carbon dioxide
    • 0.0012% Neon
    • 0.0010% Water vapor
  • Other trace gases make up less than 0.003%.

Atmospheric Layers

  • Atmospheric layers are classified based on temperature variation with altitude.
  • The main layers include:
    • Troposphere: Temperature decreases with altitude. Weather occurs here. Ranges from 6 km (4 miles) at the poles to 18 km (11 miles) at the equator.
    • Stratosphere: Temperature increases with altitude. Contains the ozone layer. Extends from the tropopause to about 31 miles (50 km) above Earth's surface.
    • Mesosphere: Temperature decreases with altitude. Meteors burn up here. Extends from about 31 miles to 50 miles (80 km)
    • Thermosphere/Ionosphere: Temperature increases rapidly with altitude. Very thin, contains very little matter. Extends from about 50 miles (80 km) to 350 miles (560 km)

Atmospheric Temperature

  • Air temperature varies significantly with altitude.
  • Troposphere: Gradual decrease.
  • Stratosphere: Gradual increase due to UV radiation absorption; creates the ozone layer.
  • Mesosphere: Gradual decrease
  • Thermosphere: Rapid increase.

Atmospheric Pressure

  • Pressure is the force exerted on a given area.
  • At sea level, atmospheric pressure is about 14.7 pounds per square inch (101.3 kPa).
  • Pressure decreases with increasing altitude.
  • The standard atmosphere at sea level is a surface temperature of 59°F (15°C) and a surface pressure of 29.92 inches of mercury (760 mm Hg) or 1,013.2 mb.
  • Air pressure is measured with a barometer.
  • Gauge pressure is the reading taken from the gauge devices and is relative to the ambient pressure.
  • Absolute pressure is the sum of the available atmospheric pressure and the gauge pressure.

Atmospheric Density

  • Air is compressible.
  • Density (mass/volume) decreases with increasing altitude
  • The standard atmosphere at sea level is 1.225 kg/m³.
  • Humidity affects air density. Moist air is less dense than dry air, and the actual density will vary with both altitude and temperature variations.

Humidity

  • Humidity is the amount of water vapor in the air.
  • Humidity expresses the water vapor content of the air, typically expressed as percentage.
  • Higher temperatures can absorb more moisture resulting in higher humidity.
  • This measure is used in weather forecasting.
  • Humidity types:
    • Relative humidity: The actual amount of moisture compared to the total amount possible at a given temperature.
    • Absolute humidity: Actual amount of water vapor in a unit volume of air.
    • Dew point: The temperature at which the air cannot hold any more moisture resulting in condensation at the ground level.

Application to Aerodynamics

  • Air density has a direct effect on aircraft performance.
  • Less dense air affects power, thrust, and lift for aircraft.

Effect of Altitude on Flight

  • Altitude impacts a number of flight aspects, including ground run, climb rates, and landing distances.
  • Aircraft needs more speed with thin air to obtain enough lift-resulting in longer takeoff distance at high altitudes.

International Standard Atmosphere (ISA)

  • The ISA is a standard model of atmospheric conditions, used for calculations and comparison of aircraft performance.
  • It is based on average conditions at 45 degrees North and South latitudes assuming constant temperature up to 80,000 feet.
  • There are standardized pressure values at specific altitudes, which are presented in a table.

Q Codes

  • Q codes provide standardized atmospheric data for aircraft operations and flight.

  • QFE- Atmospheric pressure at a specific datum for the airport.

  • QNH- Atmospheric pressure at mean sea level.

  • QNE - Atmospheric pressure at sea level for the ISA.

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Physics of the Atmosphere PDF

Description

This quiz explores the concepts of atmospheric pressure, its measurement, and the effects of altitude. Topics covered include absolute and gauge pressure, air density changes with altitude, and the factors affecting atmospheric pressure. Test your understanding of these essential principles of physics.

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