Fluid Mechanics 1000+ MCQ with answer for IIFT

1. The surface tension of mercury at normal temperature compared to that of water is
A. More
B. Less
C. Same
D. More or less depending on size of glass tube
Answer : A

2. A metal with specific gravity of a floating in a fluid of same specific gravity a will
A. Sink to bottom
B. Float over fluid
C. Partly immersed
D. Be fully immersed with top surface at fluid surface
Answer : D

3. Non uniform flow occurs when
A. The direction and magnitude of the velocity at all points are identical
B. The velocity of successive fluid particles, at any point, is the same at successive periods of time
C. Velocity, depth, pressure, etc. change from point to point in the fluid flow.
D. The fluid particles move in plane or parallel planes and the streamline patterns are identical in each plane
Answer : C

4. The body will float if the force of buoyancy is __________ the weight of the liquid displaced.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : C

5. The divergent portion of a Venturimeter is made longer than convergent portion in order to
A. Avoid the tendency of breaking away the stream of liquid
B. To minimise frictional losses
C. Both (A) and (B)
D. None of these
Answer : C

6. The resultant of all normal pressures acts
A. At C.G. of body
B. At center of pressure
C. Vertically upwards
D. At metacentre
Answer : C

7. In order to avoid tendency of separation at throat in a Venturimeter, the ratio of the diameter at throat to the diameter of pipe should be
A. 1/16 to 1/8
B. 1/8 to 1/4
C. 1/4 to 1/3
D. 1/3 to 1/2
Answer : D

8. The loss of head due to friction in a pipe of uniform diameter in which a viscous flow is taking place, is (where RN = Reynold number)
A. 1/R_N
B. 4/R_N
C. 16/R_N
D. 64/R_N
Answer : C

9. When the Mach number is between __________ the flow is called super-sonic flow.
A. 1 and 2.5
B. 2.5 and 4
C. 4 and 6
D. 1 and 6
Answer : D

10. Which of the following meters is not associated with viscosity?
A. Red wood
B. Say bolt
C. Engler
D. Orsat
Answer : D

11. According to Darcy's formula, the loss of head due to friction in the pipe is (where f = Darcy's coefficient, l = Length of pipe, v = Velocity of liquid in pipe, and d = Diameter of pipe)
A. flv²/2gd
B. flv²/gd
C. 3flv²/2gd
D. 4flv²/2gd
Answer : D

12. Euler's dimensionless number relates the following
A. Inertial force and gravity
B. Viscous force and inertial force
C. Viscous force and buoyancy force
D. Pressure force and inertial force
Answer : D

13. All the terms of energy in Bernoulli's equation have dimension of
A. Energy
B. Work
C. Mass
D. Length
Answer : D

14. A flow in which each liquid particle has a definite path, and the paths of individual particles do not cross each other, is called
A. Steady flow
B. Uniform flow
C. Streamline flow
D. Turbulent flow
Answer : C

15. The loss of head due to viscosity for laminar flow in pipes is (where d = Diameter of pipe, l = Length of pipe, v = Velocity of the liquid in the pipe, ? = Viscosity of the liquid, and w = Specific weight of the flowing liquid)
A. 4?vl/wd²
B. 8?vl/wd²
C. 16?vl/wd²
D. 32?vl/wd²
Answer : D

16. A thick liquid like syrup has a __________ viscosity than a light liquid like water.
A. Lesser
B. Greater
C. Same
D. None of these
Answer : B

17. Bulk modulus of a fluid is the ratio of
A. Shear stress to shear strain
B. Increase in volume to the viscosity of fluid
C. Increase in pressure to the volumetric strain
D. Critical velocity to the viscosity of fluid
Answer : C

18. A compound pipe of diameter d1, d2 and d3 having lengths l1, l2 and l3 is to be replaced by an equivalent pipe of uniform diameter d and of the same length (l) as that of the compound pipe. The size of the equivalent pipe is given by
A. l/d² = (l?/d?²) + (l?/d?²) + (l?/d?²)
B. l/d³ = (l?/d?³) + (l?/d?³) + (l?/d?³)
C. l/d? = (l?/d??) + (l?/d??) + (l?/d??)
D. l/d? = (l?/d??) + (l?/d??) + (l?/d??)
Answer : D

19. True one-dimensional flow occurs when
A. The direction and magnitude of the velocity at all points are identical
B. The velocity of successive fluid particles, at any point, is the same at successive periods of time
C. The magnitude and direction of the velocity do not change from point to point in the fluid
D. The fluid particles move in plane or parallel planes and the streamline patterns are identical in each plane
Answer : A

20. The pressure measured with the help of a Piezometer tube is in
A. N/mm2
B. N/m2
C. Head of liquid
D. All of these
Answer : C

21. Which of the following statement is wrong?
A. A flow whose streamline is represented by a curve is called two dimensional flow.
B. The total energy of a liquid particle is the sum of potential energy, kinetic energy and pressure energy.
C. The length of divergent portion in a Venturimeter is equal to the convergent portion.
D. A pitot tube is used to measure the velocity of flow at the required point in a pipe.
Answer : C

22. One cubic metre of water weighs
A. 100 litres
B. 250 litres
C. 500 litres
D. 1000 litres
Answer : D

23. A tank of uniform cross-sectional area (A) containing liquid upto height (H1) has an orifice of cross-sectional area (a) at its bottom. The time required to bring the liquid level from H1 to H2 will be
A. 2A × ?H?/C_d × a × ?(2g)
B. 2A × ?H?/C_d × a × ?(2g)
C. 2A × (?H? - ?H?)/C_d × a × ?(2g)
D. 2A × (?H^3/2 - ?H3/2)/C_d × a × ?(2g)
Answer : C

24. The center of gravity of the volume of the liquid displaced by an immersed body is called
A. Metacentre
B. Center of pressure
C. Center of buoyancy
D. Center of gravity
Answer : C

25. The horizontal component of buoyant force is
A. Negligible
B. Same as buoyant force
C. Zero
D. None of the above
Answer : C

26. The buoyancy depends upon the
A. Weight of the liquid displaced
B. Pressure with which the liquid is displaced
C. Viscosity of the liquid
D. Compressibility of the liquid
Answer : A

27. The property of a fluid which enables it to resist tensile stress is known as
A. Compressibility
B. Surface tension
C. Cohesion
D. Adhesion
Answer : C

28. An internal mouthpiece is said to be running free if the length of the mouthpiece is __________ the diameter of the orifice.
A. Less than twice
B. More than twice
C. Less than three times
D. More than three times
Answer : C

29. The value of the coefficient of compressibility for water at ordinary pressure and temperature in kg/cm is equal to
A. 2100
B. 2700
C. 10,000
D. 21,000
Answer : D

30. The flow in a pipe is neither laminar nor turbulent when Reynold number is
A. Less than 2000
B. Between 2000 and 2800
C. More than 2800
D. None of these
Answer : B

31. The flow in which the velocity vector is identical in magnitude and direction at every point, for any given instant, is known as
A. One dimensional flow
B. Uniform flow
C. Steady flow
D. Turbulent flow
Answer : B

32. An open vessel of water is accelerated up an inclined plane. The free water surface will
A. Be horizontal
B. Make an angle in direction of inclination of inclined plane
C. Make an angle in opposite direction to inclination of inclined plane
D. Any one of above is possible
Answer : C

33. A pitot tube is used to measure the
A. Velocity of flow at the required point in a pipe
B. Pressure difference between two points in a pipe
C. Total pressure of liquid flowing in a pipe
D. Discharge through a pipe
Answer : A

34. Coefficient of contraction is the ratio of
A. Actual velocity of jet at vena contracta to the theoretical velocity
B. Loss of head in the orifice to the head of water available at the exit of the orifice
C. Loss of head in the orifice to the head of water available at the exit of the orifice
D. Area of jet at vena-contracta to the area of orifice
Answer : D

35. A flow is called sub-sonic, if the Mach number is
A. Less than unity
B. Unity
C. Between 1 and 6
D. More than 6
Answer : A

36. When a cylindrical vessel containing liquid is revolved about its vertical axis at a constant angular velocity, the pressure
A. Varies as the square of the radial distance
B. Increases linearly as its radial distance
C. Increases as the square of the radial distance
D. Decreases as the square of the radial distance
Answer : A

37. The capillary rise at 20°C in a clean glass tube of 1 mm bore containing water is approximately
A. 5 mm
B. 10 mm
C. 20 mm
D. 30 mm
Answer : D

38. Coefficient of resistance is the ratio of
A. Actual velocity of jet at vena-contracta to the theoretical velocity
B. Area of jet at vena-contracta to the area of orifice
C. Loss of head in the orifice to the head of water available at the exit of the orifice
D. Actual discharge through an orifice to the theoretical discharge
Answer : C

39. Viscosity of water in comparison to mercury is
A. Higher
B. Lower
C. Same
D. Higher/lower depending on temperature
Answer : A

40. The liquid used in manometers should have
A. Low density
B. High density
C. Low surface tension
D. High surface tension
Answer : D

41. Mach number is significant in
A. Supersonics, as with projectiles and jet propulsion
B. Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
C. Simultaneous motion through two fluids where there is a surface of discontinuity, gravity force, and wave making effects, as with ship's hulls
D. All of the above
Answer : A

42. When an internal mouthpiece is running free, the discharge through the mouthpiece is: (where a = Area of mouthpiece, and H = Height of liquid above the mouthpiece)
A. 0.5 a. ?2gH
B. 0.707 a. ?2gH
C. 0.855 a. ?2gH
D. a. ?2gH
Answer : A

43. The unit of surface tension is
A. N/m
B. N/m²
C. N/m³
D. N-m
Answer : A

44. The ratio of absolute viscosity to mass density is known as
A. Specific viscosity
B. Viscosity index
C. Kinematic viscosity
D. Coefficient of viscosity
Answer : C

45. A differential manometer is used to measure
A. Atmospheric pressure
B. Pressure in pipes and channels
C. Pressure in Venturimeter
D. Difference of pressures between two points in a pipe
Answer : D

46. Uniform flow occurs when
A. The direction and magnitude of the velocity at all points are identical
B. The velocity of successive fluid particles, at any point, is the same at successive periods of time
C. The magnitude and direction of the velocity do not change from point to point in the fluid
D. The fluid particles move in plane or parallel planes and the streamline patterns are identical in each pleasure
Answer : C

47. According to equation of continuity,
A. w₁a₁ = w₂a₂
B. w₁v₁ = w₂v₂
C. a₁v₁ = a₂v₂
D. a₁/v₁ = a₂/v₂
Answer : C

48. An odd shaped body weighing 7.5 kg and occupying 0.01 m3 volume will be completely submerged in a fluid having specific gravity of
A. 1
B. 1.2
C. 0.8
D. 0.75
Answer : D

49. The coefficient of discharge for an external mouthpiece is
A. 0.375
B. 0.5
C. 0.707
D. 0.855
Answer : D

50. A streamline is defined as the line
A. Parallel to central axis flow
B. Parallel to outer surface of pipe
C. Of equal velocity in a flow
D. Along which the pressure drop is uniform
Answer : C