47 Questions
Which of the following is true about the density of the atmosphere with increased altitude?
The density decreases
What happens to pressure with increased altitude?
Pressure decreases
Which of the following best describes relative humidity?
The ratio of actual water vapor to saturated water vapor
If the temperature remains constant and the absolute humidity decreases, what will happen to the relative humidity?
It will increase
If the temperature increases and the absolute humidity remains constant, what will happen to the relative humidity?
It will decrease
Which of the following statements about absolute humidity is true?
Absolute humidity is the amount of water vapor in a mixture of air and water.
What happens to the amount of water vapor the air is capable of holding with increasing temperature, assuming constant pressure?
The amount of water vapor increases.
When is air said to be saturated with water vapor?
When it has all the water vapor it can hold at the prevailing temperature and pressure.
Which of the following best describes the dew point?
The temperature at which water vapor begins to condense on a surface
Why do people wearing eyeglasses experience moisture collecting on their glasses when transitioning from cold outside air to a warm room?
The glasses are below the dew point temperature of the air in the room
How is the dew point determined?
By cooling the air until water vapor condenses on its surface
What is vapor pressure and how is it related to atmospheric pressure?
Vapor pressure is the portion of atmospheric pressure exerted by moisture in the air. There is a direct relationship between vapor pressure and atmospheric pressure.
What is the dew point and how does it depend on vapor pressure?
The dew point is the temperature at which the air becomes saturated with water vapor. The dew point depends on the amount of water pressure present, which is directly related to vapor pressure.
Explain the relationship between relative humidity, absolute humidity, and temperature.
The relative humidity is the ratio of the amount of water vapor in the air to the maximum amount it could hold at a given temperature. Absolute humidity is the actual amount of water vapor in the air. As temperature increases, the maximum amount of water vapor the air can hold also increases, causing the relative humidity to decrease if the absolute humidity remains constant.
What are the four forces acting on an airplane during flight?
The four forces acting on an airplane during flight are lift, weight, thrust, and drag.
What is lift and what creates it?
Lift is the upward force created by the wing of an airplane.
What is drag and what causes it?
Drag is the friction caused by the air flowing around the airplane.
What is Bernoulli's principle and how does it relate to the study of airflow and aviation concepts?
Bernoulli's principle states that as the velocity of a fluid increases, the static pressure of that fluid will decrease, provided there is no energy added or taken away. This principle is applied in the study of air as it flows through converging or diverging passages, and is relevant to aviation concepts.
Who discovered the concept of subsonic airflow and pressure differentials?
Daniel Bernoulli, a Swiss physicist, discovered the basic concept of subsonic airflow and the resulting pressure differentials.
What is a direct application of Bernoulli's principle?
A direct application of Bernoulli's principle is the study of air as it flows through either a converging or a diverging passage, and relating the findings to some aviation concepts.
In the venturi, velocity decreases and static pressure increases.
False
The air flowing over the top of the wing moves at a greater velocity than the air flowing along the bottom.
True
The difference in static pressures between the top and bottom of the wing creates lift.
True
According to Newton's third law, for every force there is an equal and opposite __________ force.
reacting
The reacting force created by the air traveling around a wing and leaving the trailing edge is called __________.
lift
To calculate lift based on Newton's third law, Newton's second law and the formula 'Force = Mass × Acceleration' would be used. The mass would be the weight of air flowing over the wing every second, and the acceleration would be the change in velocity the wing imparts to the __________.
air
The air is forced to move in a downward direction when it travels around a wing and leaves the trailing edge because a force is required to make something change direction, according to Newton's third law. This force is the equal and opposite __________ force.
reacting
Bernoulli's principle and Newton's third law can both be used to explain the lift being created by a wing. While Bernoulli's principle focuses on the change in __________ along the wing, Newton's third law emphasizes the equal and opposite reacting force.
pressure
What is the angle of attack?
The angle between the chord line and the relative wind
What is the aspect ratio of a wing?
The relationship between the span and the chord of the wing
What happens to lift on a wing when the angle of attack becomes too great?
The lift is destroyed
Which of the following devices can be considered an airfoil?
All of the above
What is the purpose of the camber on an airfoil?
To increase velocity of the air on the top surface
What is the angle between the chord line and the longitudinal axis of the airplane called?
Angle of incidence
What is the purpose of washout in the design of an airplane's wing?
To improve the stall characteristic of the wing
What is the relationship between aspect ratio and drag on a wing?
Higher aspect ratio produces less drag
What is the initial flow of the boundary layer over the airfoil called?
Laminar layer
What is the main reason for the boundary layer to adhere to the wing surface?
Air viscosity
Which statement best describes the boundary layer as it approaches the center of the wing?
It loses speed due to skin friction and becomes thicker and turbulent.
What is the point at which the boundary layer changes from laminar to turbulent called?
The transition point
What happens to the transition point as the speed and angle of attack of the wing increase?
It tends to move forward.
Which of the following best describes wingtip vortices?
The air beneath the wing flows over the wingtip and creates a spiral or vortex that trails behind the wingtip.
What is the significance of wake turbulence caused by wingtip vortices?
It can cause a smaller airplane following too closely to be thrown out of control.
Which flight control causes the airplane to move around the longitudinal axis?
Ailerons
What is the center of gravity also referred to as?
Center of rotation
What flight control causes the airplane to move around the lateral axis?
Elevator
What is the movement described as when the airplane moves around the vertical axis?
Yaw
Test your knowledge on the relationship between altitude, temperature, pressure, and density in the atmosphere. Learn why density decreases as altitude increases in this informative quiz.
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