## Aerodynamics Questions and Answers Part-1

1. Which of the following is most difficult to analyze?
a) solid
b) plasma
c) fluids
d) cannot be determined

Explanation: Because fluid (liquid and gas) is a “squishy” substance. While the solid body is geometrically well defined and hence its motion can be defined easily. Whereas, in fluids, it is difficult to decide the qualitatively model the motion of the fluid.

2. By the time the vehicle reaches the surface of the earth, the potential and kinetic energy become zero.
a) True
b) False

Explanation: During re-entry, near the outer edge of the atmosphere, the vehicle has a large amount of kinetic energy due to its high velocity and a large amount of potential energy due to its altitude but as it reaches the surface of earth it becomes zero because the kinetic and potential energy is utilized in heating the body and heating the airflow around the body.

3. Which of the following has similar characteristics?
a) solid and liquid
b) liquid and gas
c) solid and gas
d) cannot be determined

Explanation: When force is applied to liquid and gas, there will be an increasing deformation, proportional to the rate of change of deformation. Also, the molecules in liquid and gas are loosely packed. When filled in a container, they take the shape of that container.

4. Which of the following is a point property?
a) Pressure
b) Mass
c) Density
d) Pressure and density

Explanation: Both pressure and density vary from one point to another. Pressure and density vary with the altitude and are directly proportional to each other. Pressure and density does depend on a path as they change from one point to other. If one parameter is changed, it affects pressure and density.

5. Which of the following flow is best suited for space shuttle?
a) continuum flow
b) free molecular flow
c) turbulent flow
d) laminar flow

Explanation: In free molecular flow, the gas molecules are spaced so far apart that collisions with the body surface occur only infrequently and the body surface can feel distinctly each molecular impact which reduces the vibration in the space vehicle.

6. Which of the following flow is practically impossible in nature?
a) viscous flow
b) inviscid flow
c) laminar flow
d) turbulent flow

Explanation: The flow without friction, thermal conduction, or diffusion is practically impossible. During any process or flow, the energy losses take place which leads to frictional losses, thermal losses, diffusion and various other losses.

7. In which of the following does the shock wave form?
a) subsonic flow
b) transonic flow
c) supersonic flow
d) incompressible flow

Explanation: Supersonic flows are characterized by the presence of shock waves across which the flow properties and streamlines change discontinuously. In supersonic flow, the gas can be compressed using shock waves.

8. Continuity equation is one of the most fundamental equations in fluid dynamics.
a) True
b) False

Explanation: Continuity equation relates aerodynamic phenomena over a finite region of space without being concerned about the details of precisely what is happening at a given distinct point in the flow.

9. Surface forces includes _________
a) pressure and shear stress
b) point force
c) body force
d) gravity