Aerodynamics - Fundamental Principles And Equations Quiz(MCQ)

1 .

Which of the following has similar characteristics?

A)

liquid and gas

B)

solid and gas

C)

solid and liquid

D)

cannot be determined

Correct Answer : 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.

2 .

Which of the following is most difficult to analyze?

A)

solid

B)

fluids

C)

plasma

D)

cannot be determined

Correct Answer : fluids

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.

3 .

Which of the following flow is best suited for space shuttle?

A)

laminar flow

B)

turbulent flow

C)

continuum flow

D)

free molecular flow

Correct Answer : free molecular 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.

4 .

Which of the following is a point property?

A)

Mass

B)

Density

C)

Pressure

D)

Pressure and density

Correct Answer : 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 .

Surface forces includes _________

A)

gravity

B)

point force

C)

pressure and shear stress

D)

body force

Correct Answer : pressure and shear stress

Explanation : Pressure force and shear stress acts on the complete surface of the body which means that the surface force acts on the surface and not on a point or the body. Surface forces may act either on external or on an internal surface of the body.

6 .

In which of the following does the shock wave form?

A)

supersonic flow

B)

subsonic flow

C)

transonic flow

D)

incompressible flow

Correct Answer : supersonic 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.

7 .

Which of the following flow is practically impossible in nature?

A)

laminar flow

B)

inviscid flow

C)

viscous flow

D)

turbulent flow

Correct Answer : 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.

8 .

The aircraft fly in the atmosphere due to which of the following principle?

A)

Bernoulli's principle

B)

Gravitational force

C)

Archimedes principle

D)

Newton’s law of viscosity

Correct Answer : Bernoulli's principle

Explanation : Bernoulli’s principle states that the sum of all the forms of energy (potential energy, kinetic energy, internal energy) remains constant. Only the weight of the body and the pressure forces act on the body.

9 .

Reynold's number is the ratio of _______

A)

Inertia force to gravity force

B)

Viscous force to inertia force

C)

Pressure force to inertia force

D)

Inertia force to viscous force

Correct Answer : Inertia force to viscous force

Explanation : Reynold’s number is given by Re = VL ρ / μ, which signifies the inertia to viscous force occurring in a flow. ρ / μ is called as kinematic viscosity of the fluid. Larger Reynold’s number, greater will be the inertial effects.

10 .

What is a suitable flow model for a fluid?

A)

Molecular approach

B)

Finite control volume approach

C)

Infinitesimal fluid element approach

D)

All the three models can be used based on the need

Correct Answer : All the three models can be used based on the need

Explanation : The finite control volume considers a finite volume which may be either fixed in space or moving along a fluid. The infinitesimal small element considers a finite element which may be either fixed or moving along with the flow. The molecular approach is a microscopic approach and can be applied to atoms and molecules.

11 .

Length, Scale and Volume fall under which of the following flow similarity?

A)

Dynamic Similarity

B)

Kinematic Similarity

C)

Geometric Similarity

D)

Dimensionless number

Correct Answer : Geometric Similarity

Explanation : Geometric similarity occurs when the model and prototype have same dimensional ratio in each direction. These ratios are called as scale ratio. For ex, Length scale ratio Lr = Lm/Lp where, m and p represent model and prototype.

12 .

Interia force falls under which flow similarity?

A)

Kinematic Similarity

B)

Dynamic Similarity

C)

Geometric Similarity

D)

Dimensionless number

Correct Answer : Dynamic Similarity

Explanation : For a dynamic similarity, the model and prototype must be geometrically and kinematically similar along with the condition of total sum of forces acting at a point on model and prototype must be equal. Inertia force satisfies the condition and hence it falls under dynamic similarity.

13 .

Which of the following can attribute the flow of jet of oil in an unbroken stream?

A)

Surface tension

B)

Capillarity

C)

Density

D)

Temperature

Correct Answer : Surface tension

Explanation : In a jet of oil, the molecules at the surface and the free layer differs because of which the oil resists the external force. The cohesive nature of the oil molecules helps to increase the surface area of the oil.

14 .

Which of the following is an example of Newtonian fluid?

A)

Gel

B)

Plastic

C)

Water

D)

Colloids

Correct Answer : Water

Explanation : The fluids which obey Newton’s law of viscosity are Newtonian fluids. It states that the applied shear stress is directly proportional to the amount of deformation.
τ = μdv/dy
Where, μ—–viscosity of the fluid
τ—-shear stress
dv/dy -velocity gradient.

15 .

Continuity equation is related to _______

A)

Velocity change

B)

Energy conservation

C)

Momentum conservation

D)

Mass conservation

Correct Answer : Mass conservation

Explanation : Continuity equation is related to mass conservation. It states that the total mass entering a body is equal to the total mass leaving a body.
Mass entering the body = mass leaving the body.

16 .

The quantity specifying the flow or motion is termed as _________

A)

Flux

B)

Field

C)

Density

D)

Electrostatic force

Correct Answer : Flux

Explanation : Flux is also referred to as flux density. It is the amount of quantity (q) which is flowing per unit volume(v). The quantity should have the ability to move or flow.

17 .

In electromagnetic theory, continuity equation relates _______

A)

Mass conservation

B)

Charge conservation

C)

Volume conservation

D)

Energy conservation

Correct Answer : 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=- ρ/t
Where J-current density and ρ-charge density.

18 .

For an incompressible flow, the mass continuity equation changes to ________

A)

remains same

B)

energy equation

C)

momentum equation

D)

volume continuity equation

Correct Answer : volume continuity equation

Explanation : ∇.u=0 – In this equation, u is flow velocity and it states that the divergence of flow velocity is zero. Since the flow is incompressible, the density remains constant and thus the volume cannot be changed.

19 .

The differential form of continuity equation is _________

A)

ρ=0

B)

Dv/Dt=0

C)

ρ/t + ∇.(ρV)=0

D)

∇.u=constant

Correct Answer : ρ/t + ∇.(ρV)=0

Explaination : ρ-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.

20 .

Mass can neither be created nor be destroyed is the principle of_______

A)

Energy equation

B)

Continuity equation

C)

Bernoulli's principle

D)

Momentum equation

Correct Answer : Continuity equation

Explanation : Continuity equation is based on the conservation of mass. According to this law, for any system, the amount of mass always remains constant unless and until the mass is added or removed from the system. This means that the quantity of matter does not change.

21 .

The equation which results in the change in pressure with change in the vertical height is called as __________

A)

energy equation

B)

continuity equation

C)

hydrostatic equation

D)

momentum equation

Correct Answer : hydrostatic equation

Explanation : dp = -g ρ dy represents the hydrostatic equation where p is pressure acting on a body, g is acceleration due to gravity, dy is changed in vertical height. The net force on the element acts only in the vertical direction. The pressure force on the front and back faces are equal and opposite and hence cancel.

22 .

Conservation of energy is based on which law of thermodynamics?

A)

First law of thermodynamics

B)

Second law of thermodynamics

C)

Third law of thermodynamics

D)

None of the above

Correct Answer : First law of thermodynamics

Explanation : First law of thermodynamics states that energy can neither be created nor be destroyed but it can be converted from one form to another.

23 .

The formula for kinetic energy is __________

A)

KE = 0.5*m*v

B)

KE = 0.5*m*v²

C)

KE = m*v²

D)

KE = 0.6*m*v²

Correct Answer : KE = 0.5*m*v²

Explanation : It is product of mass and square of velocity. Kinetic energy comes in picture in case of moving objects and also for the objects which has certain mass. It is defined as the work needed to accelerate a body from its rest to the moving condition.

24 .

A body moves 5m in a forward direction and then comes back to the same position. Which of the following energy does it have?

A)

Kinetic energy

B)

Potential energy

C)

Impulsive energy

D)

Sum of kinetic energy plus potential energy

Correct Answer : Kinetic energy

Explanation : A moving object always has kinetic energy. When a body will move in a forward direction, it will gain some kinetic energy which will be the product of mass and square of velocity. A body in motion always store kinetic energy in it.

25 .

The SI unit of kinetic energy is ___________

A)

Pascal

B)

Newton

C)

Meters

D)

Joules

Correct Answer : Joules

Explanation : The formula for kinetic energy is 0.5*m*v². The dimensional formula for kinetic energy is kg*(m/s)², which may be defined as 1 joule. 1 joule = kg*m²/s². 1 Joule is defined as the energy transferred to an object when the force of 1 Newton is acted on a body through a distance of 1 meter.

26 .

Determine the kinetic energy of the body of mass 90 kg moving with a speed of 200 m/s.

A)

15000 Joules

B)

21000 Joules

C)

40000 Joules

D)

900000 Joules

Correct Answer : 900000 Joules

Explanation : KE=0.5*m*v².
Substitute the values in the formula.
Here, m=90 kg and v= 200 m/s.
On solving the above equation we get,
KE=0.5*90*(200)²= 900000 Joules.

27 .

In a thermodynamic system, the measurement of heat is called as ________

A)

Entropy

B)

Heat transfer

C)

Enthalpy

D)

Internal energy

Correct Answer : Enthalpy

Explanation : Enthalpy is the total heat content in the system. It is an extensive property and is the sum of internal energy plus the product of pressure and volume.
H = U+ p*V

28 .

The energy equation, the total energy is equal to the sum of _______

A)

Kinetic energy + potential energy

B)

Kinetic energy + pressure energy

C)

Pressure energy + potential energy

D)

Kinetic energy + potential energy + pressure energy

Correct Answer : Kinetic energy + potential energy + pressure energy

Explanation : The total energy is the sum of kinetic energy plus potential energy plus internal energy. Where kinetic energy is given by 0.5 m*v2 where m is the mass and v is the velocity. Potential energy is given by PE=mgh where, m is the mass, g is the acceleration due to gravity and h is the height. The internal energy is denoted by ‘I’.

29 .

The smoke particles coming out from the chimney falls under _______

A)

Path line

B)

Streakline

C)

Streamline

D)

Position vector

Correct Answer : Streakline

Explanation : Streakline is defined as the locus of the particle that has earlier passed through the fixed point. In the case of the chimney, the chimney is the fixed point and the smoke which passes through it makes the locus. The path of the smoke can be traced.

30 .

Which of the following are the imaginary lines?

A)

Only streamline

B)

Streamline and pathline

C)

Pathline and streakline

D)

Streamline and streakline

Correct Answer : Streamline and pathline

Explanation : Both Streamlines and pathline are imaginary because streamline represents the direction of the fluid flow from a particular point in the fluid flow domain. This point can be anywhere in the fluid domain and is imaginary. Pathline is the path traced by a fluid element at a given interval of the time.

31 .

Seeta used a closed curve as her start point, it will result in the ________

A)

plane

B)

stream line

C)

stream surface

D)

stream plane

Correct Answer : stream surface

Explanation : If a curve, line or closed curve is used as a start point then the streamlines so obtained are called a stream surface. In this case, Stream function comes into the picture which defines the scalar function of these streamlines.

32 .

Which of the following is not related to the streamlines?

A)

Mass

B)

Velocity

C)

Fluid flow

D)

Fluid domain

Correct Answer : Mass

Explanation : Mass is not related to the streamlines because the velocity does not have normal component, it flows in a straight direction and does not have any normal components either and hence, the mass cannot cross the streamline.

33 .

In steady state flow, the equation for streamline can be given by ________

A)

x=0

B)

y=0

C)

x=y

D)

x=-1

Correct Answer : x=y

Explanation : In steady flow, the velocity does not change with respect to time. Hence, the velocity remains constant that is dy/dx=y/x. On integrating the above equation we get, x=y, which proves that pathline and streamline are same for steady flow with same velocity field.

34 .

In an unsteady flow, the equation of streamline is given by _____

A)

x=0

B)

y=0

C)

x=y

D)

y=x^t

Correct Answer : y=x^t

Explaination : Consider the velocity vector, V= xi +y*tj
Here u=x and v=y*t
We know that dx/u=dy/v=dz/w
On substituting the vales and integrating, we get, y=x^t.

35 .

The rate of change of angular position of the body is called as _________

A)

Distance

B)

Angular velocity

C)

Angular acceleration

D)

Angular displacement

Correct Answer : Angular velocity

Explanation : Angular velocity comes in the picture when the flow is rotational that is the flow which has both translational as well as rotational motion. It is the rate of change of angular displacement. It is denoted by omega and its SI unit id radian per second.

36 .

The angular velocity can be given by _____________

A)

ω = 0.5(dθ₁/dt + dθ₂/dt)

B)

ω = (dθ₁/dt + dθ₂/dt)

C)

ω = 4(dθ₁/dt + dθ₂/dt)

D)

ω = 8(dθ₁/dt + dθ₂/dt)

Correct Answer : ω = 0.5(dθ₁/dt + dθ₂/dt)

Explaination : Angular velocity is defined as the average of the angular velocities of the lines (2D or 3D). This is the case of 2D flow. Consider a flow, let dθ₁/dt be the x component of velocity and dθ₂/dt be the y component of velocity.

37 .

The term 2*ω is called as __________

A)

Velocity

B)

Vorticity

C)

Divergence

D)

Angular velocity

Correct Answer : Vorticity

Explaination : Vorticity is twice the angular velocity. The angular velocity of the fluid plays an important role in theoretical aerodynamics and 2*ω occurs frequently and in order to reduce the complexity, we use vorticity.

38 .

The curl of velocity equals to ______

A)

velocity

B)

pressure

C)

angular velocity

D)

vorticity

Correct Answer : vorticity

Explanation : The curl of velocity and the vorticity for a 3D flow is the same. Therefore, the curl of velocity equals to the vorticity of the 3D flow element. The equation can be defined by 2*ω = ∇*V where ∇*V – curl of velocity and 2*ω is the vorticity.

39 .

If ∇*V is not equal to zero, then the flow is _______

A)

steady

B)

unsteady

C)

rotational

D)

irrotational

Correct Answer : rotational

Explaination : In rotational flow, the fluid element has a finite angular velocity which means the element can undergo rotation and as well as distortion. The amount of distortion depends on the velocity field.

40 .

If ∇*V is equal to zero, then the flow is _________

A)

steady

B)

unsteady

C)

irrotational

D)

rotational

Correct Answer : irrotational

Explaination : In irrotational flow, the fluid element does not have a finite angular velocity which means the element cannot undergo rotation and as well as distortion. The motion of the fluid element is purely translational motion.

41 .

The absence of vorticity means the flow is ________

A)

steady

B)

unsteady

C)

rotational

D)

irrotational

Correct Answer : irrotational

Explanation : The absence of vorticity means the flow is irrotational flow, which simplifies the flow analysis. This is greatly used in case of inviscid flows. The flow analysis becomes easy for irrotational flow since there is no rotational motion of the fluid element.

42 .

The subsonic flow over an airfoil is an example of __________

A)

irrotational

B)

steady

C)

unsteady

D)

rotational

Correct Answer : irrotational

Explanation : For the subsonic flow over an airfoil, the flow is irrotational which means the motion of the fluid element is translational. In such cases, a thin boundary layer is formed around the surface. In this boundary layer, the flow is highly rotational whereas, outside the boundary layer it is irrotational.

43 .

The line integral of a closed curve around of a velocity field is defined as___________

A)

Vorticity

B)

Circulation

C)

Dilatation

D)

Streamline

Correct Answer : Circulation

Explanation : Circulation is the line integral of the velocity around a closed curve in the flow. It depends on the velocity field and the selection of the curve. It defines the movement of the flow inside the curve. It is given by-
Γ=?c V. ds where, Γ- circulation, ?c – curve, V.ds – velocity field.

44 .

If the flow is irrotational everywhere within the contour of integration then the circulation is ___________

A)

zero

B)

positive

C)

negative

D)

None of the above

Correct Answer : zero

Explanation : In the case of irrotational flow, the circulation about a curve is equal to the vorticity integrated over any open surface bounded by the curve. This leads to the result that if the flow is irrotational everywhere, the circulation is zero.

45 .

The component of vorticity normal to dS is equal to __________

A)

zero

B)

circulation

C)

circulation per unit area

D)

negative of circulation per unit area

Correct Answer : negative of circulation per unit area

Explanation : The relation between circulation and vorticity can be given by-
(∇*V).n = -dΓ/dS
Where dS – infinitesimal area enclosed
C – Infinitesimal curve.

46 .

Circulation is referred to as _________

A)

velocity

B)

velocity field

C)

divergence of velocity

D)

flux of vorticity

Correct Answer : divergence of velocity

Explanation : Using Stoke’s theorem, the line integral of velocity field along a closed curve is equal to the surface integral of velocity field along a closed path normal to the area covered by the path. But we know that curl of velocity is called vorticity and hence, the circulation is called a flux of vorticity.

47 .

Which of the following has more viscosity?

A)

Oil

B)

Honey

C)

Juice

D)

Water

Correct Answer : Honey

Explanation : Honey has more viscosity. Viscosity is the measure of the resistance offered by the flow to the shear or tensile stress. The relative motion between the two surfaces moving with different velocities is given by viscosity.

48 .

The boundary layer is formed at the ____________

A)

edges of an object

B)

surface of an object

C)

boundary of an object

D)

at a point on an object

Correct Answer : boundary of an object

Explanation : The boundary layer is formed at the boundary of an object. The boundary layer divides the flow into two parts- Viscous and inviscid. The flow inside the boundary layer is highly viscous whereas, the flow outside the boundary is inviscid flow.

49 .

In microscopic view, Circulation is a __________ quantity.

A)

scalar

B)

vector

C)

dimension less

D)

non-measurable

Correct Answer : scalar

Explanation : In a macroscopic view, circulation is a scalar quantity as it is defined as the line integral of velocity field over a closed region. In a microscopic view, circulation is a flux of vorticity, which makes it a vector quantity.

50 .

The nature of the boundary layer depends on __________

A)

Viscosity

B)

Inertia force

C)

Mach number

D)

Reynold’s number

Correct Answer : Reynold’s number

Explanation : The nature of the boundary layer depends on Reynold’s number which is the ratio of inertial force to viscous force. Depending on the value of Reynold’s number, the boundary layer may be laminar (the flow is continuous) or it may be turbulent ( the flow is discontinuous).