Unit 4 Review

Forces are vectors because __________.

• they have magnitude and direction
• they involve gravity

• they have length and width

• they can point in two directions

Which best describes Newton’s Third Law of Motion?

• 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 __________.

• 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

The reaction of downwash causes a downward reaction according to Newton’s Third Law of Motion.

• True

• False

Which of the following is true for an airplane in steady flight? Select all that apply.

• 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?

• 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?

• 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.

Increasing an airplane’s wing area will __________. Select all that apply.

• reduce pressure below the wing

• increase drag

• increase lift

• increase the camber

If the velocity of an airplane is doubled, the lift will _________.

• increase by a factor of 2

• increase by a factor of 4

• decrease by a factor of 4

• decrease by a factor of 2