Aerospace Midterm Uno

45

In the absence of frictional air drag, a ballistic trajectory achieves the longest horizontal distance at what launch angle (in degrees)?

Hydrostatic

What is the name of the equation that relates pressure change with height in a static fluid? 

a. Hydrostatic

b. Hyposometric

c. Bernoulli

d. Euler

Manometer

What device is commonly used to measure pressure differences in wind-tunnel experiments?

a. Thermometer

b. Barometer

c. Manometer

d. Anemometer

zero

What is the assumed velocity of air in the standard atmosphere model?

a. Variable

b. Based on wind speed

c. Equal to aircraft velocity

d. Zero

Mean sea level

Which of the following conditions is used as the base for the standard atmosphere?

a. Sea ice level

b. Mountain altitude

c. Mean sea level

d. Average cloud height

Temperature

What remains constant in an isothermal atmospheric layer?

a. pressure

b. temperature

c. density

d. none of the above

Linearly

In a gradient layer, how does temperature typically vary with altitude?

a. Exponentially

b. Linearly

c. Logarithmically

d. It stays constant

Altitude where air density matches standard atmosphere

What does the density altitude represent?

a. Altitude with equal temperature

b. Altitude where airspeed equals ground speed

c. Altitude where air density matches standard atmosphere

d. Altitude measured by GPS

Exponentially

How does pressure vary with altitude?

a. Exponentially

b. Linearly

c. Logarithmically

d. It stays constant

Temperature

In an ideal gas, the speed of sound depends on which variable?

a. Pressure

b. Density

c. Viscosity

d. Temperature

e. Velocity

Surface of the Earth is the hottest. As alt. increases, temp. decreases. 

Why does the temperature of the troposphere (the lowest layer of the atmosphere) typically decrease with altitude?

To meet mission-specific lift and drag needs

Why do aircraft designers choose specific airfoil shapes?

a. To increase manufacturing simplicity

b. To meet mission‑specific lift and drag needs

c. To reduce aircraft cost

d.  To increase fuel consumption

e.  To accommodate fuel tanks

velocity increases

According to the continuity equation, for an incompressible fluid (like air at Ma < 0.3) what happens when the stream‑tube area is reduced?

a. Velocity increases

b. Pressure increases

c. Mass flow increases

d. Density increases

Viscous shear force

In inviscid flow analysis, which of the following forces is neglected?

a. Pressure force

b. Magnetic force

c. Viscous shear force

d. Gravitational force

Its static pressure decreases

According to Euler’s equation, what happens when a fluid’s velocity increases?

a. Its total pressure increases

b. Its density increases

c. Its temperature increases

d. Its static pressure decreases

100 m/s

At what maximum velocity is Bernoulli’s equation generally accurate for air?

a. 30 m/s

b. 100 m/s

c. 150 m/s

d. 330 m/s

Incompressibility 

Which key assumption allows Bernoulli’s equation to be easily integrated?

a. Compressibility

b. Irregular velocity

c. Incompressibility

d. High viscosity

Dynamic pressure

What does the velocity‑squared term in Bernoulli’s equation represent?

a. Static pressure

b. Potential energy

c. Total pressure

d. Dynamic pressure

Pilot tube, static ports, and pressure indicator

What are the components of a basic airspeed indicator system?

a. Pitot tube, static ports, and pressure indicator

b. Static port and thermometer

c. Static port and pressure sensor

d. Pitot tube and airfoil

It avoid disturbing airflow around the model

Why might engineers prefer placing static ports outside the test section? 

a. It gives a better airspeed reading

b. It avoids disturbing airflow around the model

c. It helps cool the tunnel walls

d. It reduces noise

When velocity reaches 99% of the freestream velocity 

At what point is the outer edge of a boundary layer typically defined?

a. When pressure equals the freestream pressure

b. When velocity reaches 50 % of maximum freestream velocity

c. When density becomes constant

d. When velocity reaches 99% of the freestream velocity

Delays separation and reduces profile drag

How does increasing Reynolds number generally affect boundary layer behavior?

a. Promotes early separation

b. Increases pressure drag

c. Delays separation and reduces profile drag

d. Decreases turbulence

Stall

What is the angle of attack called where the lift coefficient peaks?

None of the above

Which of the following best describes the airfoil lift coefficient (C_l)?

a. Ratio of drag to weight

b. Ratio of the lift force to the dynamic pressure times chord length

c. Wing span times the velocity

d. Ratio of Area of the airfoil over the average chord length

e. None of the above

A straight line from leading to trailing edge

What is the chord line of an airfoil?

a. A line connecting two streamlines

b. A curve showing camber

c. A straight line from leading to trailing edge

d. The outer boundary of the airfoil

e. All the above

Unequal pressure at front and rear

What causes pressure drag on a body?

a. Unequal pressure at front and rear

b. Viscous stresses at the surface of the body

c. Compressibility effects

d. Surface roughness

The airspeed giving the same dynamic pressure at sea level

What does equivalent airspeed represent?

a. The airspeed in still air

b. The airspeed corrected for instrument error

c. The airspeed giving the same dynamic pressure at sea level

d. The airspeed of the ground relative to the wind

e. None of the above

In the boundary layer

Where do the viscous effects in a flow over a wing occur?

a. At the leading edge

b. In the freestream

c. At the trailing edge. 

d. At stagnation points

e. In the boundary layer

Lower momentum transfer across adjacent layers

Why do laminar boundary layers have lower skin‑friction drag compared to turbulent ones?

a. Higher viscous stresses

b. Higher momentum transfer across adjacent layers

c. Lower momentum transfer across adjacent layers

d. Laminar flow is faster than turbulent flow over the surface

Velocity divided by the speed of sound 

The Mach number is defined as:

a. Speed of sound divided by the indicated airspeed

b. Speed of sound times the indicated airspeed

c.  The square root of the product of the gas constant times the temperature

d. Velocity divided by the speed of sound

e. Ratio of the density times the velocity times a length divided by the viscosity

Flow over a cylindrical cross-sectional strut

Where might an engineer mostly likely desire a turbulent boundary layer?

a. Over a streamlined wing.

b. Flow over a cylindrical cross-sectional strut.

Allows high-energy air to flow over the upper surface

What feature of slotted flaps helps delay flow separation?

A. Only increases wing area

B. Directs flow downward

C. Allows high-energy air to flow over the upper surface

D. Reduces weight

Increase wing area and camber

What is the purpose of Fowler flaps in wing design?

A. Reduce drag

B. Increase wing area and camber

C. Reduce pressure gradient

D. Move CG forward

Delays stall by lowering pressure on the upper surface

What aerodynamic benefit is gained from vortex formation due to strakes?

A. Reduces lift

B. Delays stall by lowering pressure on the upper surface

C. Reduces drag

D. Changes AoA

Tornado-like vortex

What flow structure is created by strong vortices from strakes?

A. Turbulent sheet

B. Laminar stream

C. Tornado-like vortex

D. Diffused wake

C_D = C_D0 + kC_L²

What is the drag polar formula for total aircraft drag coefficient?

A. C_D = C_L² / AR

B. C_D = C_D0 + kC_L²

C. C_D = C_D0 + C_Di

D. C_D = C_L + C_M