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Flashcards in Aerodynamics 1 Deck (134)
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Define Scalar

A quantity expressing only magnitude (e.g. Time, amount of money, volume of a body)


Define Vector

A quantity the expresses both magnitude and direction. A vector quantity is represented by an arrow that displays direction and has a length proportional to magnitude.


Define Mass

(m) The quantity of molecular material that comprises an object


Define Volume

The size of the mass, or the amount of space occupied by an object


Define Density

(ρ) Mass per unit volume


Define Force

Mass times Acceleration; A vector quantity equal to the push or pull exerted on a body. By Newton's second law, a force is a function of an acceleration and the mass of the body.


Define Weight

The force at which a mass is attracted toward the center of the earth by gravity


Define Moment

A tendency to cause rotation around a point or axis, as a control surface around its hinge or an airplane around its center of gravity; the measure of this tendency, equal to the product of the force and perpendicular distance between the point of rotation and the direction of the force., expressed as a vector. Also called torque.


Define Work

(W) Work is done when a force acts on a body and it moves. Work is a scalar quantity measured in ft.-lbs. W=F x s


Define Power

(P) The rate of doing work, or work per unit time. Measured in ft.-lbs./sec or horsepower.


Define Energy

The ability or capacity to do work. Expressed in ft.-lbs.


Define Potential Energy

(PE) The ability of a body to do work because of its position or physical state.


Define Kinetic Energy

(KE) The ability of a body to do work because of its motion.


Explain Newton's Law of Equilibrium

Newton's First Law. "A body at rest tends to remain at rest and a body in motion tends to remain in motion in a straight line at a constant velocity unless acted upon by some unbalanced force."


State the requirements for an airplane to be in equilibrium flight

Equilibrium flight exists when the sum of all forces and the sum of all moments around the center of gravity are equal to zero. This may occur during straight and level, climbing, or descending flight so long as there is no change in flight path.


State the requirements for an airplane to be in trimmed flight

Trimmed flight exists when the sum of all moments around the center of gravity is equal to zero. The sum of all forces around the center of gravity may not be equal to zero. This may occur in a constant rate turn.


Explain Newton's Law of Acceleration

Newton's Second Law. "An unbalanced force (F) acting on a body produces an acceleration (a) in the direction of the force that is directly proportional to the force and inversely proportional to the mass (m) of the body." equation: a=F/m. (e.g. when the airplanes thrust is greater than its drag, the excess thrust will accelerate the airplane until drag increases to equal thrust)


Explain Newton's Law of Interaction

Newton's Third Law. "For every action there is an equal and opposite reaction; the forces of two bodies on each other are always equal and are directed in opposite directions." (e.g. The rearward force from a propeller's propwash causes an aircraft to move forward with an equal amount of force)


Define Static Pressure

(Ps) The weight of a column of air over a given area; the pressure each air particle exerts on another due to the weight of all the particles above; the potential energy per unit volume.


Define Air Density

(ρ) The total mass of air particles per unit volume


Define Temperature

A measure of the average kinetic energy of air particles, expressed in degrees (°C), Fahrenheit (°F), or Kelvin (K).


Define Lapse Rate

The rate that temperature decreases as you increase in altitude. (usually 2 °C per 1000 ft until about 36,000 ft) From about 36,000 ft through 66,000 feet the air remains at a constant -56.5 °C. This is called the isothermal layer.


Define Humidity

The amount of water vapor in the air


Describe the relationship between humidity and air density

As humidity increases, density decreases. This is because water molecules have less mass but displace the same number of air molecules.


Define Viscosity

(µ) A measure of a fluid's resistance to flow and shearing.


Describe the relationship between temperature and viscosity

Air viscosity increases when temperature increases.


Define local speed of sound

The rate at which sound waves travel through a particular air mass.


Describe the relationship between temperature and local speed of sound

As air temperature increases, the speed of sound increases.


State the values for standard atmosphere

  • Static Pressure (Ps0) = 29.92 in. Hg. (1013.25 mbar)
  • Temperature (T0) = 59 °F (15 °C)
  • Average Lapse Rate = 3.57 °F / 1000 ft. (2°C / 1000 ft)


Describe the General Gas Law, given static pressure, air density, temperature, and altitude

The standard gas law sets the relationship between the three properties of air: pressure (P), density (ρ), and temperature (T). R is the constant for any given gas. P=ρRT (e.g. if density remains constant and temperature increases, then pressure will increase)