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MCQOPTIONS
This section includes 176 Mcqs, each offering curated multiple-choice questions to sharpen your Fluid Mechanics and Hydraulic Machinery knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Consider the turbulent flow of a fluid through a circular pipe of diameter D.Identify the correct pair of statements. I. The fluid is well-mixed II. The fluid is unmixed III.ReD < 2300 IV. ReD > 2300 |
| A. | I and III |
| B. | II and IV |
| C. | II and III |
| D. | I and IV |
| Answer» E. | |
| 2. |
Match the following P: Compressible flowU: Reynolds numberQ: Free surface flowV: Nusselt numberR: Boundary layer flowW:Weber numberS: Pipe flowX: Froude numberT: Heat convectionY: Mach numberZ: Skin friction coefficient |
| A. | P-U; Q-X; R-V; S-Z; T-W |
| B. | P-W; Q-X; R-Z; S-U; T-V |
| C. | P-Y; Q-W; R-Z; S-U; T-X |
| D. | P-Y; Q-X; R-Z; S-U; T-V |
| Answer» E. | |
| 3. |
The Newtonian fluid has the following velocity field: = x y + 2xy ĵ - yz k The rate shear deformation yz at the point x = 2, y = 1 and z = 2 for the given flow is |
| A. | 6 |
| B. | 2 |
| C. | 12 |
| D. | 4 |
| Answer» B. 2 | |
| 4. |
Water enters a circular pipe of length L = 5.0 m and diameter D = 0.20 m with Reynolds number ReD = 500. The velocity profile at the inlet of the pipe is uniform while it is parabolic at the exit. The Reynolds number at the exit of the pipe is_____ |
| A. | 577 |
| B. | 500 |
| C. | 520 |
| D. | 5.00 |
| Answer» C. 520 | |
| 5. |
For the laminar flow of water oyer a sphere, the drag coefficient CF is defined as CF = F/( U D ), where F is the drag force, is the fluid density, U is the fluid velocity and D is the diameter of the sphere. The density of water is 1000 kg/m . When the diameter of the sphere is 100 mm and the fluid velocity is 2 m/ s, the drag coefficient is 0.5. If water now flows over another sphere of diameter 200 mm under dynamically similar conditions, the drag force (in N) on this sphere is _______. |
| A. | 100N |
| B. | 18N |
| C. | 20N |
| D. | 40N |
| Answer» D. 40N | |
| 6. |
Velocity vector of a flow field is given as = 2xy - x zĵ. The vorticity vector at (1, 1, 1) is |
| A. | 4 - ĵ |
| B. | 4 - k |
| C. | - 4ĵ |
| D. | - 4k |
| Answer» E. | |
| 7. |
The viscous laminar flow of air over a flat plate results in the formation of a boundary layer. The boundary layer thickness at the end of the plate of length L is L. When the plate length is increased to twice of its original length, the percentage change in Iaminar boundary layer thickness at the end of the plate (with respect to L) is ________ |
| A. | 44.42% |
| B. | 41.42% |
| C. | 43.42% |
| D. | 40.42% |
| Answer» C. 43.42% | |
| 8. |
A fluid flow is represented by the velocity field = ax + ay&jcirc;, where a is a constant. The equation of stream line passing through a point (1, 2) is |
| A. | x 2y = 0 |
| B. | 2x + y = 0 |
| C. | 2x y = 0 |
| D. | x + 2y = 0 |
| Answer» D. x + 2y = 0 | |
| 9. |
Water flows through two different pipes A and B of the same circular cross-section but at different flow rates. The length of pipe A is 1.0 m and that of pipe B is 2.0 m. The flow in both the pipes is laminar and fully developed. If the frictional head loss across the length of the pipes is same, the ratio of volume flow rates QB /QA is _____ (round off to two decimal places) |
| A. | 0.5 |
| B. | 0.4 |
| C. | 0.6 |
| D. | 0.3 |
| Answer» B. 0.4 | |
| 10. |
Water (density = 1000 kg/m3) at ambient temperature flows through a horizontal pipe of uniform cross-section at the rate of 1 kg/s. If the pressure drop across the pipe is 100 kPa, the minimum power required to pump the water across the pipe, in Watt, is _______. |
| A. | 100 Watt |
| B. | 150 Watt |
| C. | 50 Watt |
| D. | 200 Watt |
| Answer» B. 150 Watt | |
| 11. |
A pump handling a liquid raises its pressure from 1 bar to 30 bar. Take the density of the liquid as 990 kg/m3. The isentropic specific work done by the pump in kJ/kg is |
| A. | 0.10 |
| B. | 0.30 |
| C. | 2.50 |
| D. | 2.93 |
| Answer» E. | |
| 12. |
An ideal water jet with volume flow rate of 0.05 m3/s strikes a flat plate placed normal to its path and exerts a force of 1000 N. Considering the density of water as 1000 kg/m3, the diameter (in mm) of the water jet is ______. |
| A. | 56.41 mm |
| B. | 55.41 mm |
| C. | 66.41 mm |
| D. | 76.41 mm |
| Answer» B. 55.41 mm | |
| 13. |
The velocity profile inside the boundary layer for flow over a plate is given as (u / u ) = sin{( /2)(y/ )} , where U is the free stream velocity and is the local boundary layer thickness. If * is the local displacement thickness, the value of ( * / ) is |
| A. | 0 |
| Answer» C. | |
| 14. |
If x is the distance measured from the leading edge of a flat plate, then laminar boundary layer thickness varies as |
| A. | 1/x |
| B. | x |
| C. | x |
| D. | x |
| Answer» E. | |
| 15. |
An aluminium alloy (density 2600 kg/m3) casting is to be produced. A cylindrical hole of 100 mm diameter and 100 mm length is made in the casting using sand core (density 1600 kg/m3). The net buoyancy force (in Newton) acting on the core is _______. |
| A. | 7.7 N. |
| B. | 8.7 N. |
| C. | 6.7 N. |
| D. | 9.7 N. |
| Answer» B. 8.7 N. | |
| 16. |
The SI unit of kinematic viscosity v is |
| A. | m /s |
| B. | kg/ms |
| C. | m/s |
| D. | m |
| E. | /s |
| Answer» B. kg/ms | |
| 17. |
For a two-dimensional flow, the velocity field is u =xi +yjx + y x + y where i and j are the basis vectors in the x y Cartesian coordinate system. Identify the CORRECT statements from below. 1. The flow is incompressible 2. The flow is unsteady 3. y-component of acceleration, ay = - y(x + y ) 4. x-component of acceleration, ax = -(x + y)(x + y ) |
| A. | 2 and 3 |
| B. | 1 and 3 |
| C. | 1 and 2 |
| D. | 3 and 4 |
| Answer» C. 1 and 2 | |
| 18. |
Consider the following statements regarding streamline(s): (i) It is a continuous line such that the tangent at any point on it shows the velocity vector at that point (ii) There is no flow across streamlines (iii) dx=dy= dzis the differential equation of a streamline, where u, v and w are velocities in directions x, y and z, respectivelyuvw(iv) In an unsteady flow, the path of a particle is a streamline Which one of the following combinations of the statements is true? |
| A. | (i), (ii), (iv) |
| B. | (ii), (iii), (iv) |
| C. | (i), (iii), (iv) |
| D. | (i), (ii), (iii) |
| Answer» E. | |
| 19. |
The necessary and sufficient condition which brings about separation of boundary layer is dp> 0 (True / False)dx |
| A. | True |
| B. | False |
| C. | NA |
| D. | NA |
| Answer» B. False | |
| 20. |
The instantaneous stream wise velocity of a turbulent flow is given as follows: u(x, y, z, t) = u(x, y, z) + u'(x, y, z, t) The time average of the fluctuating velocity u (x, y, z, t) is |
| A. | |
| B. | zero |
| Answer» D. | |
| 21. |
The velocity field of an incompressible flow is given by V = (a1x + a2y + a3 z)i + (b1x + b2y + b3 z)j + (c1x + c2y + c3 z)k, where a1 = 2 and c3 = 4. The value of b2 is _________. |
| A. | 2 |
| B. | 1 |
| C. | 3 |
| D. | 0 |
| Answer» B. 1 | |
| 22. |
A cube of side 100 mm is placed at the bottom of an empty container on one of its faces. The density of the material of the cube is 800 kg/m3. Liquid of densit y 1000 k g/m3 is now poured into the container. The minimum height to which the liquid needs to be poured into the container for the cube to just lift up is _____ mm. |
| A. | h 80 mm |
| B. | h 70 mm |
| C. | h 75 mm |
| D. | h 81 mm |
| Answer» B. h 70 mm | |
| 23. |
A test is conducted on a one-fifth scale model of a Francis turbine under a head of 2 m and volumetric flow rate of 1 m3/s at 450 rpm. Take the water density and the acceleration due to gravity as 103 kg/m3 and 10 m/s2, respectively. Assume no losses both in model and prototype turbines. The power (in MW) of a full sized turbine while working under a head of 30 m is _______ (correct to two decimal places). |
| A. | 29.25 |
| B. | 30.26 |
| C. | 29.05 |
| D. | 29 |
| Answer» D. 29 | |
| 24. |
Which of the following statements are TRUE, when the cavitation parameter = 0? i. the local pressure is reduced to vapor pressure ii. cavitation starts iii. boiling of liquid starts iv. cavitation stops |
| A. | i, ii and iv |
| B. | only ii and iii |
| C. | only i and iii |
| D. | i, ii and iii |
| Answer» E. | |
| 25. |
Consider two hydraulic turbines having identical specific speed and effective head at the inlet. If the speed ratio (N1 /N2) of the two turbines is 2, then the respective power ratio (P1 /P2) is ____. |
| A. | 0.26 |
| B. | 0.24 |
| C. | 0.25 |
| D. | 0.35 |
| Answer» D. 0.35 | |
| 26. |
Oil flows through a 200 mm diameter horizontal cast iron pipe (friction factor, f = 0.0225) of length 500 m, The volumetric flow rate is 0.2 m3/s, The head loss (in m) due to friction is (assume g = 9.81 m/s2) |
| A. | 116.18 |
| B. | 0.116 |
| C. | 18.22 |
| D. | 232.36 |
| Answer» B. 0.116 | |
| 27. |
Water flows through a 10 mm diameter and 250 m long smooth pipe at an average velocity of 0.1 m/s. The density and the viscosity of water are 997 kg/m3 and 855 10 6 Ns/m2, respectively. Assuming fully- developed flow, the pressure drop (in Pa) in the pipe is ____? |
| A. | 6840 pascal |
| B. | 680 pascal |
| C. | 4844 pascal |
| D. | 9840 pascal |
| Answer» B. 680 pascal | |
| 28. |
A smooth pipe of diameter 200 mm carries water. The pressure in the pipe at section S1 (elevation: 10 m) ie 50 kPa, At section S2 (elevation: 12 m) the pressure is 20 kPa and velocity is 2 m/s. Density of water is 1000 kg/m3 and acceleration due to gravity is 9.8 ms 2, Which of the following is TRUE |
| A. | flow is from S1 to S2 and head loss is 0.53 m |
| B. | flow is from S2 to S1 and head loss is 0.53 m |
| C. | flow is from S1 to S2 and head loss is 1.06 m |
| D. | flow is from S2 to S1 and head loss is 1.06 m |
| Answer» D. flow is from S2 to S1 and head loss is 1.06 m | |
| 29. |
A velocity field is given as VV 3x yi 6xyzk where x, y, z are in m and V in m/s. Determine if (i) It represents an incompressible flow (ii) The flow is irrotational (iii) The flow is steady |
| A. | (ii) |
| B. | (i) |
| C. | (i) and (ii) |
| D. | (iii) |
| Answer» B. (i) | |
| 30. |
The difference in pressure (in N/m2) across an air bubble of diameter 0.001 m immersed in water (surface tension = 0.072 N/m) is_____. |
| A. | 88 N/m |
| B. | 288 N/m |
| C. | 28 N/m |
| D. | None of these |
| Answer» C. 28 N/m | |
| 31. |
In a Pelton wheel, the bucket peripheral speed is 10 m/s, the water jet velocity is 25 m/s and volumetric flow rate of the jet is 0.1 m3/s. If the jet deflection angle is 120 and the flow is ideal, the power developed is |
| A. | 7.5 kW |
| B. | 15.0 kW |
| C. | 22.5 kW |
| D. | 37.5 kW |
| Answer» D. 37.5 kW | |
| 32. |
An incompressible fluid (kinematic viscosity, 7.4 10 7 m /s, specific gravity, 0.88) is held between two parallel plates. If the top plate is moved with a velocity of 0.5 m/s while the bottom one is held stationary, the fluid attains a linear velocity profile in the gap of 0.5 mm between these plates: the shear stress in Pascals on the surface of top plate is |
| A. | 0.651 10 |
| B. | 0.651 |
| C. | 6.51 |
| D. | 0.651 10 |
| E. | |
| Answer» C. 6.51 | |
| 33. |
At a hydro electric power plant site, available head and flow rate are 24.5 m and 10.1 m3/s respectively. If the turbine to be installed is required to run at 4.0 revolution per second (rps) with an overall efficiency of 90%, the suitable type of turbine for this site is |
| A. | Francis |
| B. | Kaplan |
| C. | Pelton |
| D. | Propeller |
| Answer» B. Kaplan | |
| 34. |
Oil in a hydraulic cylinder is compressed from an initial volume 2 m3 to 1.96 m3. If the pressure of oil in the cylinder changes from 40 MPa to 80 MPa during compression, the bulk modulus of elasticity of oil is |
| A. | 1000 MPa |
| B. | 2000 MPa |
| C. | 4000 MPa |
| D. | 8000 MPa |
| Answer» C. 4000 MPa | |
| 35. |
Match List-I with List-II and select the correct answer using the codes given below the lists: List-IList-IIP. Curtis1. Reaction steam turbine Q. Rateau 2. Gas turbine R. Kaplan3. Velocity compounding S. Francis 4. Pressure compounding 5. Impulse water turbine 6. Axial turbine 7. Mixed flow turbine 8. Centrifugal pump |
| A. | P - 2 , Q - 1 , R - 1 , S - 6 |
| B. | P - 3 , Q - 4 , R - 6 , S - 7 |
| C. | P - 1 , Q - 3 , R - 1 , S - 5 |
| D. | P - 3 , Q - 4 , R - 7 , S - 6 |
| Answer» C. P - 1 , Q - 3 , R - 1 , S - 5 | |
| 36. |
The ratio Vm/u0 is |
| A. | 1 |
| Answer» D. | |
| 37. |
The head loss for a laminar incompressible flow through a horizontal circular pipe is h1. Pipe length and fluid remaining the same, if the average flow velocity doubles and the pipe diameter reduces to half its previous value, the head loss is h2. The ratio h2 /h1. is |
| A. | 1 |
| B. | 4 |
| C. | 8 |
| D. | 16 |
| Answer» D. 16 | |
| 38. |
For a fully developed flow of water in a pipe having diameter 10 cm, velocity 0.1 m/s and kinematic viscosity 10 5 m2/s, the value of Darcy friction factor is ________. |
| A. | 0.364 |
| B. | 0.264 |
| C. | 0.064 |
| D. | 0.164 |
| Answer» D. 0.164 | |
| 39. |
For a two-dimensional in compressible flow field given by u = A(x i yj ), where A > 0, which one of the following statements is FALSE? A. It satisfies continuity equation B. It is unidirectional when x 0 and y . C. Its streamlines are given by x = y. D. It is irrotational |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 40. |
In a Lagrangian system, the position of a fluid particle in a flow is described as x = x0e kt and y = y0ekt where t is the time while x0, y0, and k are constants. The flow is |
| A. | unsteady and one-dimensional |
| B. | steady and two-dimensional |
| C. | steady and one-dimensional |
| D. | unsteady and two-dimensional |
| Answer» C. steady and one-dimensional | |
| 41. |
Consider a fully developed steady laminar flow of an in compressible fluid with viscosity . through a circular pipe of radius R, Given that the velocity at a radial location of R/2 from the centerline of the pipe is U1, the shear stress at the wall is K U1 /R, where K is _______. |
| A. | 3.21 |
| B. | 5.24 |
| C. | 6.24 |
| D. | None of these |
| Answer» E. | |
| 42. |
Consider fluid flow between two infinite horizontal plates when are parallel (the gap between them being 50 mm), The top plate is sliding parallel to the stationary bottom plate at a speed of 3 m/s. The flow between the plates is solely due to the motion of the top plate. The force per unit area (magnitude) required to maintain the bottom plate stationary is ________ N/m2. Viscosity of the fluid = 0.44 kg/ms and density p = 888 kg/m3. |
| A. | 26.4 |
| B. | 26.9 |
| C. | 26.7 |
| D. | 26.8 |
| Answer» B. 26.9 | |
| 43. |
Oil (kinematic viscosity, oil = 1.0 10-6 m2/s) flows through a pipe of 0.5 m diameter with a velocity of 10 m/s. Water (kinematic viscosity, vw = 0.89 10-6 m2/s) is flowing through a model pipe of diameter 20 mm. For satisfying the dynamic similarity, the velocity of water (in m/s) is _______. |
| A. | 21.24 |
| B. | 23.25 |
| C. | 22.25 |
| D. | 22 |
| Answer» D. 22 | |
| 44. |
Air ( = 1.2 kg/m3 and kinematic viscosity, = 2 10-5 m2/s) with a velocity of 2 m/s flows over the top surface of a flat plate of length 2.5 m. If the average value of friction coefficient is Cf =1.328 Rexthe total drag force (in N) per unit width of the plate is _________. |
| A. | 0.1159 |
| B. | 0.0259 |
| C. | 0.0157 |
| D. | 0.0159 |
| Answer» E. | |
| 45. |
Which combination of the following statements about steady incompressible forced vortex flow is correct? P: Shear stress is zero at all points in the flow. Q: Vorticity is zero at all points in the flow. R: Velocity is directly proportional to the radius from the centre of the vortex. S: Total mechanical energy per unit mass is constant in the entire flow field. Select the correct answer using the codes given below: |
| A. | P and Q |
| B. | R and S |
| C. | P and R |
| D. | P and S |
| Answer» C. P and R | |
| 46. |
Match the following pairs: EquationPhysical InterpretationP. v = 0I. Incompressible continuity equationQ. . v = 0II. Steady flowR. v / t = 0III. Irrotational flowS. v / t = 0IV. Zero acceleration of fluid particle |
| A. | P-IV, Q-I, R-II, S-III |
| B. | P-IV, Q-III, FRS-II |
| C. | P-III, Q-I, R-IV, S-II |
| D. | P-III, Q-I, R-II, S-IV |
| Answer» D. P-III, Q-I, R-II, S-IV | |
| 47. |
The 2-D flow with, velocity V = (x + 2y + 2) i + (4 y) j is |
| A. | Compressible and irrotational |
| B. | Compressible and not irrotational |
| C. | In compressible and irrotational |
| D. | In compressible and not irrotational |
| Answer» E. | |
| 48. |
A fluid of dynamic viscosity 2 10 5 kg/ms and density 1 kg/m3 flows with an average velocity of 1 m/s through a long duct of rectangular (25 mm 15 mm) cross-section, Assuming laminar flow, the pressure drop (in Pa) in the fully developed region per meter length of the duct is _______. |
| A. | 180 Pa/m |
| B. | 1.8208 Pa/m |
| C. | 182.08 Pa/m |
| D. | 18208 Pa/m |
| Answer» C. 182.08 Pa/m | |
| 49. |
Neglect losses in the cylinder and assume fully developed laminar viscous flow throughout the needle: the Darcy friction factor is 64/Re. where Re is the Reynolds number. Given that the viscosity of water is 1.0 10-3 kg/ms, the force F in newtons required on the plunger is |
| A. | 0.13 |
| B. | 0.16 |
| C. | 0.3 |
| D. | 4.4 |
| Answer» D. 4.4 | |
| 50. |
Consider steady, incompressible and irrotational flow through a reducer in a horizontal pipe where the diameter is reduced from 20 cm to 10 cm. The pressure in the 20 cm pipe just upstream of the reducer is 150 kPa. The fluid has a vapour pressure of 50 kPa and a specific weight of 5 kN / m3 . Neglecting frictional effects, the maximum discharge (in m3 / s) that can pass through the reducer without causing cavitation is |
| A. | 0.05 |
| B. | 0.16 |
| C. | 0.27 |
| D. | 0.38 |
| Answer» C. 0.27 | |