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Aerodynamics Mcqs

Q:

The differential form of continuity equation is __________

A) ?.u=constant B) Dv/Dt=0
C) ?/t + ?.(?V)=0 D) ?=0
 
Answer & Explanation Answer: C) ?/t + ?.(?V)=0

Explanation: ?-density V-velocity vector t-time
The divergence represents the inflow and outflow whereas the time derivative represents the accumulation of mass inside a body. It states that the amount of mass entering the body is equal to the amount of mass leaving the body.

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217
Q:

Which of the following gives a better approximate distribution of drag over thin airfoils?
The given percentages are for skin- friction drag and pressure drag respectively.

A) 85, 15 B) 50, 50
C) 64, 35 D) Inadequate data
 
Answer & Explanation Answer: A) 85, 15

Explanation: The thin airfoils can be considered as 2-D streamlined bodies. For such cases, the drag distribution is 85% for skin-friction drag and 15% for pressure drag. This assumption is valid for thin airfoils, not always.

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202
Q:

Which of the following has similar characteristics?

A) solid and liquid B) liquid and gas
C) solid and gas D) cannot be determined
 
Answer & Explanation Answer: B) liquid and gas

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.

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115
Q:

Reynold’s number is the ratio of ____________

A) Inertia force to viscous force B) Viscous force to inertia force
C) Inertia force to gravity force D) Pressure force to inertia force
 
Answer & Explanation Answer: A) Inertia force to viscous force

Explanation: Not available for this question

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108
Q:

In the equation, ?.V=1/ v*D (v)/Dt, the term ?.V is _________

A) change in velocity B) divergence of velocity
C) volume D) velocity as a function of time
 
Answer & Explanation Answer: B) divergence of velocity

Explanation: Divergence of velocity is physically the time rate of change of the volume of a moving fluid element per unit volume where v is small volume and because of this small volume, ?.V is same throughout the volume. Moving control volume is used for the physical interpretation of the divergence of velocity.

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98
Q:

Which of the following is a point property?

A) Pressure B) Mass
C) Density D) Pressure and density
 
Answer & Explanation Answer: 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.

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97
Q:

In electromagnetic theory, continuity equation relates _______

A) Volume conservation B) Mass conservation
C) Charge conservation D) Energy conservation
 
Answer & Explanation Answer: C) Charge conservation

Explanation: In electromagnetic theory, charge conservation is a result of Maxwell’s equation which states that divergence of current density is equal to the negative rate of change of charge density.
?.J=- ?/t
Where J-current density and ?-charge density.

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97
Q:

Which of the following flow is practically impossible in nature?

A) viscous flow B) inviscid flow
C) laminar flow D) turbulent flow
 
Answer & Explanation Answer: B) inviscid 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.

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96