HI Gradians,
You have completed the syllabus of the RVUNL exam for Fluid Mechanics. Now BYJU'S Exam Prep brings you the 100 most important questions of the Fluid Mechanics subject.
Here you will find the 100 most important questions for the Fluid mechanics subject of the Mechanical Engineering syllabus. The top 10 questions are attached here rest questions you can find in the below pdf.
PDF OF 100 MOST IMPORTANT QUESTIONS OF FLUID MECHANICS
1. Mercury is used in barometer because______.
A.It has high density,
B. It has negligible capillarity effect,
C. It has very low vapour pressure
D. It has low compressibility
Ans. C
Sol.
Mercury is used in barometer because of its low vapour pressure.
So, the correct option is (c).
2. Navier-Stokes equation, Bernoulli’s Principle and Continuity equation, respectively work on the principles of conservation of___.
A. Mass, Energy, and Momentum
B. Energy, Momentum, and Mass
C. Momentum, Energy, and Mass
D. Momentum, Mass and Energy
Ans. C
Sol.
Navier-Stokes equation, Bernoulli's Principle and Continuity equation work on the principles of conservation of momentum, energy, and mass respectively.
3. If we increase the temperature, the viscosity of the gas will___.
A. Increase
B. Decrease
C. Remain constant
D. Decrease then increase
Ans. A
Sol.
The viscosity of gas will increase with an increase in temperature because as the temperature increases the kinetic energy of the molecule increase, thus resulting in the increase of frequency of collision between molecules.
4. The flow of water in a wash basin through a central opening is an example of_____.
A. Ranking vortex
B. Free vortex
C. Forced vortex
D. Rotational vortex
Ans. B
Sol.
Concept of Circulation in a Free Vortex Flow
Free Vortex Flow
- Fluid particles move in circles about a point.
- The only non-trivial velocity component is tangential.
- This tangential speed varies with radius r so that the same circulation is maintained.
- Thus, all the streamlines are concentric circles about a given point where the velocity along each streamline is inversely proportional to the distance from the centre. This flow is necessarily irrotational.
5. During the flow over a circular cylinder, the drag coefficient drops significantly at a critical Reynold’s Number of 2 ×105. This is due to____.
A.excessive momentum loss in the boundary layer.
B. separation point travelling upstream.
C. reduction in skin-friction drag.
D. the delay in separation due to transition to turbulence.
Ans. D
Sol.
The drag coefficient remains practically constant until Reynold’s number of 2 × 105 is reached. At this stage, the Cd drops steeply by a factor of 5. This is due to the fact that the laminar boundary layer turns turbulent and stays unseparated over a longer distance, then reducing the wake considerably.
6. The centre of pressure of any submerged plane vertical surface is _______
A. Always below the centroid of the surface
B. Always above the centroid of the surface
C. Always coincident with the centroid of the surface
D. Above or below the centroid depending on the area of the surface
Ans. A
Sol.
- The centre of pressure is the point where the total sum of a pressure field acts on a body, causing a force to act through that point.
- The centre of pressure of any submerged plane surface is always below the centroid of the surface.
7. Bluff body is the body of such a shape that pressure drag as compared to friction drag is_____.
A. same
B. more
C. less
D. zero
Ans. B
Sol.
- The bluff body is the body of such a shape that pressure drag as compared to friction drag is more.
- There occurs no overlapping with streamlines during the flow of liquid.
8. The vacuum pressure of water is 5.2 m. The equivalent absolute pressure is_____.
A. 9 m
B. 5.1 m
C. 5.3 m
D. 15.5 m
Ans. B
Sol.
- The vacuum pressure of water is 5.2 m= negative gauge pressure
The local atmospheric pressure of water= 10.3 m of water
Equivalent absolute pressure= -5.2 + 10.3=5.1 m of water
9. The magnitude of water hammer depends on_____.
A. length of pipe
B. elastic properties of pipe material
C. rate of stoppage of flow
D. All options are correct
Ans. D
Sol.
- A water hammer is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change).
10. In laminar flow through a round tube, the discharge varies ______.
A. linearly as the viscosity
B. Inversely as the pressure drop
C. As the cube of the diameter
D. inversely as the viscosity
Ans. D
Sol.
- Discharge is proportional to velocity and velocity is decreases with increases with viscosity means velocity is inversely proportional to viscosity and also discharge.
PDF OF 100 MOST IMPORTANT QUESTIONS OF FLUID MECHANICS
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