1.3 Lift And Drag.

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1.3 Lift And Drag. - Quiz

Ch. 3 Aerodynamics.


Questions and Answers
  • 1. 

    What will be the ratio between airspeed and lift if the angle of attack and other factors remain constant and airspeed is doubled? Lift will be

    • A.

      Four times greater.

    • B.

      The same.

    • C.

      Two times greater.

    Correct Answer
    A. Four times greater.
    Explanation
    When airspeed is doubled while keeping the angle of attack and other factors constant, the lift generated by the aircraft will increase by a factor of four. This is because lift is directly proportional to the square of the airspeed. Therefore, if the airspeed is doubled, the lift will increase by a factor of four (2^2 = 4).

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  • 2. 

    What true airspeed and angle of attack should be used to generate the same amount of lift as altitude is increased?

    • A.

      A higher true airspeed for any given angle of attack.

    • B.

      The same true airspeed and angle of attack.

    • C.

      A lower true airspeed and higher angle of attack.

    Correct Answer
    A. A higher true airspeed for any given angle of attack.
    Explanation
    As altitude increases, the air density decreases. In order to generate the same amount of lift, a higher true airspeed is required because the reduced air density provides less lift. The angle of attack remains the same because it is the angle between the wing's chord line and the oncoming airflow, and it determines the lift coefficient. Therefore, to compensate for the decreased air density, a higher true airspeed is necessary while keeping the angle of attack constant.

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  • 3. 

    What affects indicated stall speed?

    • A.

      Weight, load factor, and power.

    • B.

      Load factor, angle of attack, and power.

    • C.

      Angle of attack, weight, and air density.

    Correct Answer
    A. Weight, load factor, and power.
    Explanation
    The indicated stall speed of an aircraft is influenced by three main factors: weight, load factor, and power. Weight affects the stall speed as a heavier aircraft requires a higher airspeed to generate enough lift to overcome its weight. Load factor, which is the ratio of the lift force to the weight of the aircraft, also affects stall speed. Higher load factors increase the stall speed. Lastly, power plays a role as the amount of power available affects the aircraft's ability to maintain lift at slower speeds. Therefore, all three factors - weight, load factor, and power - impact the indicated stall speed.

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  • 4. 

    The stall speed of an airplane

    • A.

      Is affected by weight, and bank angle.

    • B.

      Is constant regardless of weight or airfoil configuration.

    • C.

      Is not affected by dynamic pressures and lift co-efficient.

    Correct Answer
    A. Is affected by weight, and bank angle.
    Explanation
    The stall speed of an airplane is affected by weight and bank angle. Weight plays a significant role in determining the stall speed as a heavier aircraft requires a higher speed to generate enough lift to counteract its weight. Additionally, bank angle affects the stall speed because when the aircraft is in a banked turn, the lift is divided into two components: one that opposes gravity and one that turns the aircraft. This reduces the effective lift available to oppose gravity, increasing the stall speed.

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  • 5. 

    What is the effect on total drag of an aircraft if the airspeed decreases in level flight below that speed for maximum L/D?

    • A.

      Drag increases because of increased induced drag.

    • B.

      Drag increases because of increased parasite drag.

    • C.

      Drag decreases because of lower induced drag.

    Correct Answer
    A. Drag increases because of increased induced drag.
    Explanation
    When the airspeed decreases below the speed for maximum lift-to-drag ratio (L/D), the angle of attack of the aircraft increases in order to maintain lift. This increased angle of attack leads to an increase in induced drag, which is the drag caused by the generation of lift. Therefore, the correct answer is that the drag increases because of increased induced drag.

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  • 6. 

    What is the relationship between induced and parasite drag when the gross weight is increased?

    • A.

      Induced drag increases more than parasite drag.

    • B.

      Parasite drag increases more than induced drag.

    • C.

      Both parasite and induced drag are equally increased.

    Correct Answer
    A. Induced drag increases more than parasite drag.
    Explanation
    When the gross weight is increased, the induced drag increases more than the parasite drag. Induced drag is the drag that is caused by the generation of lift, and it is directly related to the amount of lift being produced. As the gross weight increases, more lift needs to be generated, resulting in an increase in induced drag. On the other hand, parasite drag is the drag caused by factors such as form drag and skin friction, which are not directly related to lift. While the increase in gross weight may also lead to an increase in parasite drag, it is not as significant as the increase in induced drag.

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  • 7. 

    How does Vs (KTAS) speed vary with altitude?

    • A.

      Varies directly with altitude.

    • B.

      Remains the same at all altitudes.

    • C.

      Varies inversely with altitude.

    Correct Answer
    A. Varies directly with altitude.
    Explanation
    As altitude increases, Vs (KTAS) speed also increases. This means that the speed at which an aircraft flies true airspeed (KTAS) directly correlates with the altitude at which it is flying. As the aircraft climbs higher, the air density decreases, resulting in a decrease in aerodynamic drag. With less drag, the aircraft can maintain a higher true airspeed. Therefore, the speed varies directly with altitude.

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  • 8. 

    What is the reason for variations in geometric pitch along a propeller or rotor blade?

    • A.

      It permits a relatively constant angle of attack along its length when in cruising flight.

    • B.

      It prevents the portion of the blade near the hub or root from stalling during cruising flight.

    • C.

      It permits a relatively constant angle of incidence along its length when in cruising flight.

    Correct Answer
    A. It permits a relatively constant angle of attack along its length when in cruising flight.
    Explanation
    The reason for variations in geometric pitch along a propeller or rotor blade is to permit a relatively constant angle of attack along its length when in cruising flight. This means that the propeller or rotor blade can maintain an optimal angle to the airflow, ensuring efficient lift production and preventing stalling. By adjusting the pitch along the blade, the angle of attack can be optimized for different sections, allowing for smooth and balanced flight.

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  • 9. 

    What flight condition should be expected when an aircraft leaves ground effect?

    • A.

      An increase in induced drag requiring a higher angle of attack.

    • B.

      A decrease in parasite drag permitting a lower angle of attack.

    • C.

      An increase in dynamic stability.

    Correct Answer
    A. An increase in induced drag requiring a higher angle of attack.
    Explanation
    When an aircraft leaves ground effect, there is a decrease in the cushioning effect provided by the ground, resulting in a decrease in lift and an increase in induced drag. This increase in induced drag requires the aircraft to maintain a higher angle of attack in order to generate enough lift to stay airborne. Therefore, the correct answer is that an increase in induced drag requiring a higher angle of attack should be expected when an aircraft leaves ground effect.

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  • 10. 

    By changing the angle of attack of a wing, the pilot can control the airplane's

    • A.

      Lift, airspeed, and drag.

    • B.

      Lift, gross weight, and drag.

    • C.

      Lift and airspeed, but not drag.

    Correct Answer
    A. Lift, airspeed, and drag.
    Explanation
    By changing the angle of attack of a wing, the pilot can control the airplane's lift, airspeed, and drag. The angle of attack refers to the angle between the wing's chord line and the oncoming airflow. By adjusting this angle, the pilot can increase or decrease the lift generated by the wing. This, in turn, affects the airspeed of the aircraft. Additionally, changing the angle of attack also alters the amount of drag experienced by the airplane. Therefore, the correct answer is that the pilot can control the lift, airspeed, and drag of the aircraft by changing the angle of attack of the wing.

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  • 11. 

    At which speed will increasing the pitch attitude cause an airplane to climb?

    • A.

      High speed.

    • B.

      Low speed.

    • C.

      Any speed.

    Correct Answer
    A. High speed.
    Explanation
    Increasing the pitch attitude refers to raising the nose of the airplane. At high speeds, increasing the pitch attitude will cause the airplane to climb because the increased angle of attack generates more lift. This lift overcomes the force of gravity and allows the airplane to ascend. At low speeds, increasing the pitch attitude may cause the airplane to stall instead of climb. At any speed, increasing the pitch attitude will have an effect on the airplane's flight path, but it is at high speeds where it will result in a climb.

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  • 12. 

    How can an airplane produce the same lift in ground effect as when out of ground effect?

    • A.

      A lower angle of attack.

    • B.

      The same angle of attack.

    • C.

      A higher angle of attack.

    Correct Answer
    A. A lower angle of attack.
    Explanation
    When an airplane is in ground effect, it experiences reduced drag and increased lift due to the proximity of the ground. This is because the ground creates a cushion of air that helps to generate additional lift. To produce the same lift in ground effect as when out of ground effect, the airplane needs to adjust its angle of attack. By decreasing the angle of attack, the airplane can maintain the same lift force while benefiting from the ground effect. Therefore, the correct answer is a lower angle of attack.

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