GATE 2012 AEROSPACE ENGINEERING (Q 1-10)

1. For a symmetric airfoil, the lift coefficient for zero degree angle of attack is
   1. – 1.0
   2. 0.0
   3. 0.5
   4. 1.0

   Answer:- 0.0

2. The critical Mach number of an airfoil is attained when
   1. the freestream Mach number is sonic.
   2. the freestream Mach number is supersonic.
   3. the Mach number somewhere on the airfoil is unity.
   4. the Mach number everywhere on the airfoil is supersonic.

   Answer:- the Mach number somewhere on the airfoil is unity.

3. The shadowgraph flow visualization technique depends on
   1. the variation of the value of density in the flow.
   2. the first derivative of density with respect to spatial coordinate.
   3. the second derivative of density with respect to spatial coordinate.
   4. the third derivative of density with respect to spatial coordinate.

   Answer:- the second derivative of density with respect to spatial coordinate.

4. Hohmann ellipse used as earth-Mars transfer orbit has
   1. apogee at earth and perigee at Mars.
   2. both apogee and perigee at earth.
   3. apogee at Mars and perigee at earth.
   4. both apogee and perigee at Mars.

   Answer:- apogee at Mars and perigee at earth.