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fluid mechanics MCQs

Practise focused fluid mechanics questions with marked answers for exam preparation and subject revision.

fluid mechanics Mcqs
1. In a two dimensional incompressible steady flow around an airfoil, the stream lines are 2 cm apart at a great distance from the airfoil, where the velocity is 30 m/sec. The velocity near the airfoil, where the stream lines are 1.5 cm apart, is_________________?
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A. 90 m/sec

B. 22.5 m/sec

C. 40 m/sec

D. 33 m/sec

2. Which of the following is an incorrect statement ?
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A. Coefficient of contraction of a venturimeter is unity

B. Discharge is independent of orientation of venturimeter whether it is horizontal, vertical or inclined

C. Flow nozzle is cheaper than venturimeter but has higher energy loss

D. None of the above statement is correct.
3. Two pipes of same length and diameters d and 2d respectively are connected in series. The diameter of an equivalent pipe of same length is________________?
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A. less than d

B. between 1.5 d and 2d

C. greater than 2d

D. between d and 1.5 d

4. For a sphere of radius 15 cm moving with a uniform velocity of 2 m/sec through a liquid of specific gravity 0.9 and dynamic viscosity 0.8 poise, the Reynolds number will be_________________?
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A. 600

B. 337.5

C. 300

D. 675
5. The length of a pipe is 1 km and its diameter is 20 cm. If the diameter of an equivalent pipe is 40 cm, then its length is_____________________?
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A. 32 km

B. 8 km

C. 20 km

D. 4 km

6. Due to each end contraction, the discharge of rectangular sharp crested weir is reduced by________________?
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A. 10%

B. 15%

C. 20%

D. 5%
7. The horizontal component of force on a curved surface is equal to the_______________?
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A. weight of liquid vertically above the curved surface

B. force on a vertical projection of the curved surface

C. force on the horizontal projection of the curved surface

D. product of pressure intensity at its centroid and area

8. The ratio of average velocity to maximum velocity for steady laminar flow in circular pipes is_______________?
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A. 1/2

B. 2

C. 2-Mar

D. 3-Feb

9. If velocity is zero over l/3rd of a cross-section and is uniform over remaining 2/3rd of the cross-section, then the correction factor for kinetic energy is__________________?
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A. 27/8

B. 3-Apr

C. 9/4

D. 2-Mar

10. The pressure at the summit of a syphon is_______________?
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A. equal to atmospheric

B. more than atmospheric

C. none of the above

D. less than atmospheric
11. Hot wire anemometer is used to measure_______________?
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A. pressure intensity of liquid

B. velocity of gas

C. pressure intensity of gas

D. discharge

12. If the dynamic viscosity of a fluid is 0.5 poise and specific gravity is 0.5, then the kinematic viscosity of that fluid in stokes is__________________?
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A. 0.25

B. 1.0

C. none of the above

D. 0.5

13. Flow at constant rate through a tapering pipe is________________?
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A. non-uniform flow</strong>

B. correct answer is?

C. unsteady flow

D. uniform flow

E. steady flow
14. Coefficient of contraction for an external cylindrical mouthpiece is_________________?
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A. 0.7H

B. 1.00

C. 0.611

D. 0.855

15. Surge wave in a rectangular channel is an example of_________________?
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A. unsteady flow

B. uniform flow

C. correct answer is?

D. steady flow

E. non-uniform flow</strong>

16. Equation of continuity is based on the principle of conservation of_________________?
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A. none of the above

B. mass

C. momentum

D. energy

17. Which of the following statements is correct ?
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A. Lower critical Reynolds number is of no practical significance in pipe flow problems.

B. Upper critical Reynolds number is the number at which turbulent flow changes to laminar flow

C. Lower critical Reynolds number has the value 2000 in pipe flow

D. Upper critical Reynolds number is significant in pipe flow problems.

18. The Prartdtl mixing length is_________________?
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A. maximum at the pipe wall

B. none of the above

C. zero at the pipe wall

D. independent of shear stress

19. Stanton diagram is a______________?
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A. semi-log plot of friction factor against Reynolds number

B. semi-log plot of friction factor against relative roughness

C. log-log plot of relative roughness against Reynolds number

D. log-log plot of friction factor against Reynolds number
20. The boundary layer thickness at a distance of l m from the leading edge of a flat plate, kept at zero angle of incidence to the flow direction, is O.l cm. The velocity outside the boundary layer is 25 ml sec. The boundary layer thickness at a distance of 4 m is__________________?
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A. 0.20 cm

B. 0.10 cm

C. 0.40 cm

D. 0.05 cm