# Steam and Gas Turbines Questions and Answers – Elementary Airfoil Theory

This set of Steam and Gas Turbines Problems focuses on “Elementary Airfoil Theory”.

1. Airfoil when passed through fluids produces ______________
a) thrust
b) drag
c) thrust & drag
d) none of the mentioned

Explanation: Air foil when passed through fluids produces aerodynamic forces. Thrust and Drag forces are called as aerodynamic force.

2. In subsonic flight air foil has a shape of round at the leading edge.
a) True
b) False

Explanation: In subsonic flight air foil has a shape of round at the leading edge.

3. Air foils when designed to work in water are called as _________
a) Dynamic air foil
b) Hydro foil
c) Dynamic air foil & Hydro foil
d) None of the mentioned

Explanation: Air foils when designed to work in water are called as hydro foils. Hydro is word used to describe water.

4. In air foil lift is __________ proportional to angle of attack.
a) inversly
b) not related
c) directly
d) none of the mentioned

Explanation: In air foil lift is directly proportional to angle of attack. If angle of attack is increased its lift is increased.

5. Cambered air foils generate lift at ________ angle of attack.
a) zero
b) high
c) low
d) none of the mentioned

Explanation: Cambered air foils generate lift at zero angle of attack. While other type of air foils require some minimum angle of attack to produce lift.
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6. _________ difference is observed in between the sides of air foil.
a) Temperature
b) Pressure
c) Temperature & pressure
d) None of the mentioned

Explanation: Pressure difference is observed in between the sides of air foil. Due to fluid lines difference in both sides of the airfoil pressure difference is established.

7. Relation between angle of attack and _______ for invincible fluids is found in thin airfoil theory.
a) Lift
b) Drag
c) Lift & Drag
d) None of the mentioned

Explanation: Relation between angle of attack and lift for invincible fluids is found in thin airfoil theory.

8. Slope between lift coefficient and angle of attack in a line is __________
a) 90 degree
b) 180 degree
c) 360 degree
d) 60 degree

Explanation: Slope between lift coefficient and angle of attack in a line is 360 degrees.

9. Center of pressure lies exactly in ________ of the chord from the leading edge in a symmetrical air foil.
a) one quarter
b) half
c) three fourth
d) none of the mentioned

Explanation: Center of pressure lies exactly in one quarter of the chord from the leading edge in a symmetrical air foil.

10. Aerodynamic center lies exactly at ______ on the chord from leading edge in cambered air foil.
a) half
b) one quarter
c) three fourth
d) none of the mentioned

Explanation: Aerodynamic center lies exactly at one quarter on the chord from leading edge in cambered air foil.

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