GATE 2009 AEROSPACE ENGINEERING (Q 1-10)

1. For a flow through a Prandtl-Meyer expansion wave
   1. Mach number stays constant.
   2. Entropy stays constant.
   3. Temperature stays constant
   4. Density stays constant.

   Answer:- Entropy stays constant.

2. For two-dimensional irrotational and incompressible flows
   1. Both potential and stream functions satisfy the Laplace equation
   2. Potential function must satisfy the Laplace equation but the stream function need not.
   3. Stream function must satisfy the Laplace equation but the potential function need not
   4. Neither the stream function nor the potential function need to satisfy the Laplace equation

   Answer:- Both potential and stream functions satisfy the Laplace equation

3. A trailing edge plain flap deflected downward increases the lifrt coefficient of an airfoil by
   1. Increasing the effective camber of the airfoil.
   2. Delaying the separation of the flow from the airfoil surface.
   3. Increasing the local airspeed near the trailing edge.
   4. Controlling the growth of the boundary layer thickness along the airfoil surface

   Answer:- Increasing the effective camber of the airfoil.

4. Thin airfoil theory predicts that the lift slope is for
   1. Symmetric airfoils only
   2. Cambered airfoils only
   3. Any airfoil shape
   4. Joukowski airfoils only

   Answer:- Symmetric airfoils only

5. The ordinary differential equation where kis real and positive
   1. is non-linear
   2. has a charecteristic equation with one real and one complex root
   3. has a charecteristic equation with two real roots
   4. has a complementary function that is simple harmonic

   Answer:- has a complementary function that is simple harmonic

6. A non-trivial solution to the (n*n) system of equations [A]{x} = {0}. where {0} is the null vector
   1. can never be found
   2. may be found only if [A] is not singular
   3. may be found only if [A] is an orthogonal matrix
   4. may be found only if [A] has at least one eigenvalue equal to zero

   Answer:-