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# API Fundamentals of Aerodynamics- Chapter 1

## Terms

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Define Scalar Quantity
A quantity that represents only magnitude. e.g. time, temp, or volume.
Define Vector Quantity
A quantity that represents only magnitude and direction. e.g. displacement, velocity, acceleration, or force.
Define Force(F)
Force(F) is a push or pull exerted on a body.
Define Mass(m)
Mass(m) is the quantity of molecular material that comprises an object.
Define Volume(v)
Volume(v) is the amount of space occupied by an object.
Define Density(p)
Density (p) is mass per unit volume. Expressed p = mass/volume
Define Weight(W)
Weight(W) is the force with which a mass is attracted toward the center of the earth by gravity.
Define Moment(M)
A Moment(M) is created when a force is applied at some distance from an axis or fulcrum, and tends to produce rotation about that point.
Define Work(W)
Work(W) is done when force acts on a body and moves it. It is a scalar quantity equal to the force (F) times the distance of displacement(s). W = F x s
Define Power(P)
Power(P) is the rate of doing work or work done per unit of time.
Define Energy
Energy is a scalar measure of a body's capacity to do work. Equation for total energy is: T.E. = K.E. + P.E.
Define Potential Energy
P.E. is the ability of a body to do work because of its position or state of being. It is a function of mass(m), gravity(g), and height(h). P.E. = mgh
Define Kinetic Energy
K.E. is the ability of a body to do work because of its motion. It is a function of mass(m) and velocity(V). K.E. = 1/2(mV^2)
Define Newton's first Law of Motion - Law of Equilibrium
A body at rest tends to remain at rest and a body in motion tends to remain in motion unless acted upon by some unbalanced force
Define Newton's second Law of Motion - Law of Acceleration
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 form: a = f/m or a = (Vout - Vin)/time
Define Newton's Third Law of Motion - Law of Interaction
For every action there is an equal and opposite reaction.
(i.e. Hot gases from an engine pushing the plane forward.)
Define, compare, and contrast equilibrium and trimmed flight
Equilbrium is the absence of acceleration, linear or angular. Trimmed flight exists when the sum of the moments around the center of gravity is zero. Equilibrium exists when all forces and moments equal zero. In trimmed flight the forces may not equal zero, since you could potentially trim a plane into a turn.
Define static pressure
Static pressure(Ps) is the pressure each air particle exerts on another.
Define air density
Air density(p) is the total mass of air particles per unit of volume.
Define temperature
Temperature(T) is a measure of the average kinetic energy of the air particles.
Define lapse rate
Lapse rate: Air temperature decreases linearly with an increase in altitude at a rate of 2 degrees C(3.57 degrees F) per 1000 ft until 36,000 feet.
Define Humidity
Humidity is the amount of water vapor in the air.
Define viscosity
Viscosity(u) is a measure of the air's resistance to flow and shearing.
Define local speed of sound
Local speed of sound is the rate at which sound waves travel through a particular air mass.
State the relationship between humidity and air density
As humidity increase, air density increases. This is due to more (denser) water molecules in the air.
State the relationship between temperature and viscosity
Similar to engine oil, the hotter a fluid gets the move viscous it gets. Temp goes up, viscosity goes down.
State the relationship between temperature and the local speed of sound
As the temperature of air increases, the speed of sound increases.
State the pressure, temperature, lapse rate, and air density at sea level in the standard atmosphere using both Metric and English units of measurement
Stat Pres(Pso) 29.92 in-Hg 1013.2mb
Temp(To) 59F 15C
Avg Lapse Rate 3.57F/1K' 2C/1K'
Air Density Po .002378 slugs/ft^3 1.2255 grams/liter
Local SO Sound 661.7kts 340.4m/s
State the relationship between pressure, temperature, and air density using the General Gas Law
The relationship between air: pressure, density, and temperature is: P = pRT

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