GATE 2007 AEROSPACE ENGINEERING (Q 11-20)

  1. For a fixed center of gravity location of an airplane, when the propeller is mounted on the nose of the fuselage
    1. longitudinal static stability increases
    2. longitudinal static stability decreases
    3. longitudinal static stability remains same
    4. longitudinal static stability is maximum

    Answer:-

  2. Let an airplane in a steady level flight be trimmed at a certain speed. A level and steady flight at higher speed could be achieved by changing
    1. engine throttle only
    2. elevator only
    3. throttle and elevator together
    4. rudder only

    Answer:- elevator only
    The elevator can be used to change and control the trim of the airplane. In essence, this controls the equilibrium velocity of the airplane. For example, by a downward deflection of the elevator, a new trim angle smaller than the original trim angle can be obtained. this corresponds to an increase in velocity of the airplane.

  3. For a plane strain problem in the x-y plane, in general, the non-zero stress terms are
    1. σzz, σxz, σyz, σxy
    2. σzz, σxz, σyz, σxy
    3. σxx, σxy, σyy, σxz
    4. σxx, σyy, σxy, σzz

    Answer:-

  4. For an elastic anisotropic solid, the number of independent elastic constants in its consitutive equations is
    1. 2
    2. 9
    3. 21
    4. 36

    Answer:-

  5. Total pressure at a point is defined as the pressure when the flow is brought to rest
    1. adiabatically
    2. isentropically
    3. isothermally
    4. isobarically

    Answer:- isentropically
    Adiabtic means No heat transfer
    Isentropic means reversible adiabatic
    Isothermal means COnstant temperature
    Isobaric means constant pressure

  6. The drag divergence Mach number of an airfoil
    1. is a fixed number for a given airfoil
    2. is always higher than the critical Mach number
    3. is equal to the critical Mach number at zero angle of attack
    4. is the Mach number at which a shock wave first appears on the airfoil

    Answer:- is always higher than the critical Mach number

  7. On which one of the following thermodynamic cycles does an ideal ramjet operate?
    1. The Rankine cycle
    2. The Brayton cycle
    3. The Carnot cycle
    4. The Otto cycle

    Answer:- The Brayton cycle

  8. Across a normal shock
    1. both total temperature and total pressure decrease
    2. both total temperature and total pressure remain constant
    3. total pressure remains constant but total temperature decreases
    4. total temperature remains constant but total pressure decreases

    Answer:- total temperature remains constant but total pressure decreases
    For calorifically perfect gas, across a normal shock

    • Mach number is subsonic
    • Static pressure increases
    • Total pressure decreases
    • Static temperature increases
    • Total temperature is constant
    • Density increases
    • entropy increases
  9. The Joukowskii airfoil is studied in aerdynamics because
    1. it is used in many aircraft
    2. it is easily transformed into a circle, mathematically
    3. it has a simple geometry
    4. it has the highest lift curve slope among all aifoils

    Answer:- it is easily transformed into a circle, mathematically

  10. One of the criteria for high-speed airplanes is that the critical Mach number should be as high as possible. Therefore, high-speed subsonic airplanes are usually designed with
    1. thick airfoils
    2. thin airfoils
    3. laminar flow airfoils
    4. dimond airfoils

    Answer:- thin airfoil

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