A2.U4 Exam

Forces are vectors because __________. (4.A.3)

• they involve gravity
• they have length and width
• they have magnitude and direction
• they can point in two directions

Which best describes Newton’s Third Law of Motion? (4.A.1)

• Any object will remain at rest until an force acts on it.
• For every action there is an equal and opposite reaction.
• Any object will remain in motion until an force acts on it.
• Any force applied to an object moves the object in the same direction of the force.

Lift on a wing is most properly defined as the ____________. (4.A.2)

• differential pressure acting perpendicular to the chord of the wing
• increased pressure resulting from air flow over the upper camber of an airfoil, which acts perpendicular to the mean camber
• force acting perpendicular to the relative wind
• the force that opposes drag

True or False. The reaction of downwash causes an downward reaction according to Newton’s Third Law of Motion. (4.B.1)

• True
• False

Which of the following is true for an airplane in steady flight? Select all that apply. (4.A.3)

• The sum of all upward components of forces equals the sum of all downward components of forces
• The sum of all forward components of forces is greater than the sum of all backward components of forces
• The sum of all upward components of forces equals the sum of all forward components of forces
• The sum of all upward components of forces is greater than the sum of all downward components of forces
• The sum of all forward components of forces equals the sum of all backward components of forces

Which of the following is true relative to a changing angle of attack? (4.B.1 and 4.B.3)

• A decrease in angle of attack will increase the pressure below the wing and increase drag
• An increase in angle of attack will decrease the pressure above the wing and increase lift
• An increase in angle of attack will increase the pressure above the wing and increase drag
• An decrease in angle of attack will increase lift

The Longer Path theory (or Equal Transit Time theory) says that the molecules of air flowing over the top of a wing must travel faster than the molecules of air flowing beneath the wing in order to meet at the trailing (back) edge. What is the problem with this theory? (4.B.1)

• It assumes that molecules of air arriving at the front of the wing are divided equally above and below the wing.
• It assumes that molecules move at the same speed regardless of how fast air flows above and below the wing.
• It assumes that molecules of air arriving at the front of the wing at the same time must also arrive at the back edge of the wing at the same time.
• It assumes that more air travels above the wing than below the wing.

The __________ of an airplane can act as an airfoil by helping to produce stability and LIFT. (4.B.2)

• Propeller
• Fuselage
• Vertical Stabilizer
• All of the above

Increasing an airplane’s wing area will __________. Select all that apply. (4.B.2 and 4.E.1)

• reduce pressure below the wing
• increase drag
• increase lift
• increase the camber

If the velocity of an airplane is doubled, the lift will _________. (4.B.3)

• ncrease by a factor of 2
• increase by a factor of 4
• decrease by a factor of 4
• decrease by a factor of 2