Dgca Module 08 Basic Aerodynamics

ISA, or the International Standard Atmosphere, is a model that represents the average atmospheric conditions at sea level. It includes pressure, temperature, and density as parameters. Pressure refers to the force exerted by the atmosphere on a given area, temperature represents the average kinetic energy of the air molecules, and density refers to the mass of air per unit volume. These three parameters are crucial in understanding and predicting the behavior of the atmosphere and its impact on various phenomena, such as weather patterns, aircraft performance, and atmospheric chemistry.

The correct answer is 15 degrees Celsius because standard sea level temperature is the average temperature at sea level under normal atmospheric conditions. This average temperature is typically around 15 degrees Celsius.

Density is a physical property of a substance and is defined as the mass of the substance divided by its volume. This means that the correct answer is "Mass / Volume". The density of a substance remains constant regardless of the sample size, making it a useful property for identifying and comparing different materials.

A rocket does not depend on the density of air for its operation because it carries its own oxidizer and fuel, allowing it to operate in the vacuum of space where there is no air. In contrast, a kite relies on the density of air to generate lift, and a parachute relies on air resistance to slow down its descent. Therefore, the correct answer is rocket.

The millibar is a unit of measurement used to quantify barometric pressure. Barometric pressure refers to the pressure exerted by the Earth's atmosphere at a specific location. It is commonly used in weather forecasting and aviation to determine changes in weather patterns and altitude. The millibar scale is based on the metric system and is equal to one-thousandth of a bar, which is a unit of pressure. Therefore, the correct answer is barometric pressure.

Lapse rate refers to the rate at which temperature decreases with an increase in altitude. It is a measure of how the temperature changes vertically in the atmosphere. As one goes higher in the atmosphere, the temperature usually decreases, and this rate of decrease is known as the lapse rate. Therefore, the correct answer is temperature.

When the pressure is half of that at sea level, the altitude is 18,000 ft. This is because as altitude increases, the atmospheric pressure decreases. At sea level, the atmospheric pressure is considered to be 1 atmosphere. When the pressure is half of that, it means that the atmospheric pressure is 0.5 atmospheres. According to the standard atmospheric pressure lapse rate, this corresponds to an altitude of approximately 18,000 ft.

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Lift is generated primarily due to the pressure difference between the upper and lower surfaces of an airplane's wing. This difference is created by the wing's shape (airfoil) and its angle of attack, causing air to move faster over the top surface than the bottom surface, resulting in lower pressure above the wing and higher pressure below it. The other factors listed, such as the color of the airplane, the weight of the airplane, and its speed on the ground, do not directly influence the generation of lift.

As altitude increases, the atmospheric pressure decreases. This decrease in pressure is not constant but rather follows an exponential pattern. The higher the altitude, the faster the pressure decreases. This is because the atmosphere becomes less dense as we move higher up, resulting in a decrease in the number of air molecules and therefore a decrease in pressure.