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MCQOPTIONS
This section includes 51 Mcqs, each offering curated multiple-choice questions to sharpen your Fluid Mechanics knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Friction factor of pipes depends on |
| A. | rate of flow |
| B. | fluid density |
| C. | viscosity |
| D. | All options are correct |
| Answer» E. | |
| 2. |
A Newtonian fluid having a viscosity of 0.39 Ns/m2 and specific gravity of 0.91 flows through a 25 mm diameter pipe with velocity of 3.6 m/s. Then the value of Reynold’s number is: |
| A. | 210 |
| B. | 240 |
| C. | 175 |
| D. | 155 |
| Answer» B. 240 | |
| 3. |
For maximum power transmission through a pipe line, the frictional head loss equals |
| A. | \(\frac{H}{2}\) |
| B. | \(\frac{{3H}}{5}\) |
| C. | \(\frac{H}{4}\) |
| D. | \(\frac{H}{3}\) |
| Answer» E. | |
| 4. |
A pipeline AB of diameter 30 cm and of length 400 m carry water at the rate of 50 litres/sec. The flow takes place from A and B where point B is 30 meters above A. Pressure at B is 2 ksc. Pressure at A is (Take f = 0.008) |
| A. | 5.2 ksc |
| B. | 5.3 ksc |
| C. | 5.0 ksc |
| D. | 5.1 ksc |
| Answer» D. 5.1 ksc | |
| 5. |
For laminar flow in pipes, the momentum correction factor is : |
| A. | 1.2 |
| B. | 1.33 |
| C. | 2 |
| D. | 2.4 |
| Answer» C. 2 | |
| 6. |
In case of transmission of hydraulic power by a pipeline to a turbine in a hydroelectric power station, the maximum power transmission efficiency through the pipeline is |
| A. | 76% |
| B. | 67% |
| C. | 54% |
| D. | 42% |
| Answer» C. 54% | |
| 7. |
An orifice meter is used to measure the: |
| A. | flow rate in a pipe |
| B. | static pressure in the fluid |
| C. | atmospheric pressure |
| D. | flow pressure in the pipe |
| Answer» B. static pressure in the fluid | |
| 8. |
_____ is the point in a fluid stream where the diameter of the stream is the least, and fluid velocity is maximum. |
| A. | Vena contracta |
| B. | Critical point |
| C. | Neutral point |
| D. | Point of centre of gravity |
| Answer» B. Critical point | |
| 9. |
Energy grade line(EGL) represents the |
| A. | Elevation head |
| B. | Pressure head + elevation head |
| C. | Pressure head + velocity head + elevation head |
| D. | Pressure head + velocity head |
| Answer» D. Pressure head + velocity head | |
| 10. |
Air flows through a duct, and the Pitot-static tube measuring the velocity is attached to a differential manometer containing water. If the deflection of the manometer is 100 mm, assuming the density of air is constant and equals to 1.22 kg/m3, and that the coefficient of the tube is 0.98. The air velocity will be. |
| A. | 0.393 m/s |
| B. | 4.07 m/s |
| C. | 3.93 m/s |
| D. | 39.3 m/s |
| Answer» E. | |
| 11. |
Discharge through the main is ______ by connecting pipes in parallel. |
| A. | Increased |
| B. | Decreased |
| C. | Regulated |
| D. | Same |
| Answer» B. Decreased | |
| 12. |
If H is the total head at inlet and h is the head lost due to friction, efficiency of power transmission through a straight pipe is given by |
| A. | \(\frac{{H - h}}{H}\) |
| B. | \(\frac{H}{{H + h}}\) |
| C. | \(\frac{{H - h}}{{H + h}}\) |
| D. | \(\frac{H}{{H - h}}\) |
| Answer» B. \(\frac{H}{{H + h}}\) | |
| 13. |
Consider the following statements:1. In flow through hydro-dynamically smooth pipes, the friction factor f is always a constant.2. In flow through hydro-dynamically smooth pipes, the friction factor f is always a function of the flow Reynolds number.3. In a fully developed rough turbulent pipe flow, the friction factor f is a function of relative roughness only.4. In a fully developed rough turbulent pipe flow, the friction factor f is a function of the flow Reynolds number and relative roughness.Which of the above statements are correct? |
| A. | 1 and 3 |
| B. | 2 and 3 |
| C. | 2 and 4 |
| D. | 1 and 4 |
| Answer» C. 2 and 4 | |
| 14. |
In order to replace a pipe of diameter D by n parallel pipes of diameter d the relation used is |
| A. | \(d~=~\frac{D}{n^{\frac{2}{5}}}\) |
| B. | \(d~=~\frac{D}{n^{{2}}}\) |
| C. | \(d~=~\frac{D}{n^{\frac{3}{2}}}\) |
| D. | \(d~=~\frac{D}{n}\) |
| Answer» B. \(d~=~\frac{D}{n^{{2}}}\) | |
| 15. |
If Reynold's number is less than 1, then |
| A. | Viscous forces are very strong as compared to inertial forces |
| B. | Viscous forces are very weak as compared to inertial forces |
| C. | Viscous forces are equal to inertial forces |
| D. | Flow is turbulent in saturated soils |
| Answer» B. Viscous forces are very weak as compared to inertial forces | |
| 16. |
A 0.2 m diameter 20 km long transports oil at a flow rate of 0.01 m3/s. Calculate power required to maintain the flow if dynamic viscosity and density of oil is 0.08 Pa.s and 900 kg/m3 respectively. |
| A. | 4.064 kW |
| B. | 3.074 kW |
| C. | 4.074 kW |
| D. | 5.064 kW |
| Answer» D. 5.064 kW | |
| 17. |
In series-pipe applications |
| A. | The head losses through each pipe are added to obtain the total head loss |
| B. | The head loss is same through each pipe |
| C. | Friction factors are assumed for each pipe |
| D. | Flow increases |
| Answer» B. The head loss is same through each pipe | |
| 18. |
In turbulent flow, the loss of head is approximately proportional to |
| A. | Velocity |
| B. | (Velocity)1/2 |
| C. | (Velocity)3/4 |
| D. | (Velocity)2 |
| Answer» E. | |
| 19. |
For maximum transmission of power through a pipe with a total head, the total head loss due to friction hf is given by ________ |
| A. | H/10 |
| B. | 2H/3 |
| C. | H/2 |
| D. | H/3 |
| Answer» E. | |
| 20. |
In a laminar flow through a circular pipe of diameter 200 mm, the maximum velocity is found to be 1 m / s. The velocity at a radial distance of 50 mm from the axis of the pipe will be |
| A. | 0.50 m/s |
| B. | 0.25 m/s |
| C. | 0.75 m/s |
| D. | 1.25 m/s |
| Answer» D. 1.25 m/s | |
| 21. |
In the design of pipeline the usual practice is to assume that due to aging of pipelines:1. The effective roughness increases linearly with time.2. The friction factor increases linearly with time3. The flow through the pipe becomes linearly lesser with time.Which of the above statements is/are correct? |
| A. | 1, 2 and 3 |
| B. | 3 only |
| C. | 2 only |
| D. | 1 only |
| Answer» E. | |
| 22. |
A mouthpiece can't be used under very large head because of |
| A. | creation of vortex at vena contracta |
| B. | cavitation problem at vena contracta |
| C. | large variation of discharge |
| D. | erratic flow |
| Answer» C. large variation of discharge | |
| 23. |
According to Darcy’s formula, loss of head due to friction in the pipe isWhere f = Darcy’s coefficientl = length of pipev = velocity of liquid flowd = diameter of pipe |
| A. | \(\frac{{4{\rm{fl}}{v^2}}}{{2{\rm{gd}}}}\;\) |
| B. | \(\frac{{{\rm{fl}}{v^2}}}{{{\rm{gd}}}}\;\) |
| C. | \(\frac{{{\rm{3fl}}{v^2}}}{{{\rm{gd}}}}\;\) |
| D. | \(\frac{{{\rm{4fl}}{v^2}}}{{{\rm{gd}}}}\;\) |
| Answer» B. \(\frac{{{\rm{fl}}{v^2}}}{{{\rm{gd}}}}\;\) | |
| 24. |
If the flow rate of water in a pipeline is doubled, then the pressure drop will be _________ the original value. |
| A. | same as |
| B. | 2 times |
| C. | 4 times |
| D. | one-half of |
| Answer» C. 4 times | |
| 25. |
If the velocity of flow as well as the diameter of the flowing pipe are respectively doubled, the head loss thereafter be |
| A. | Halved |
| B. | Doubled |
| C. | Increased 4 times |
| D. | No change |
| Answer» C. Increased 4 times | |
| 26. |
In a flow of fluid through pipes, the hydraulic gradient line (HGL) is always placed |
| A. | Below the total energy line |
| B. | Below the axis of the pipe |
| C. | Sloping in nature along with flow |
| D. | Above the total energy line |
| Answer» B. Below the axis of the pipe | |
| 27. |
A and B are at the same elevation of 2.5 m above datum in the valve and pipe line as shown in the given figure. The velocity head of 0.5 m, head loss in the valve of 0.2 m and pressure head of 2.5 m are the parameters at A. The piezometric head at B is equal to: |
| A. | 5.0 m |
| B. | 5.5 m |
| C. | 5.3 m |
| D. | 4.8 m |
| Answer» E. | |
| 28. |
Maximum pressure rise due to water hammer in a pipeline (a = area of the pipe; V0 = velocity, g = acceleration due to gravity; t = time period; L = length of the pipeline) is |
| A. | \(\frac{{a{V_0}}}{{2g}}\) |
| B. | \(\frac{{aV_0^2}}{{2g}}\) |
| C. | \(\frac{{L{V_0}}}{{gT}}\) |
| D. | Independent of the dimensions of the pipe |
| Answer» D. Independent of the dimensions of the pipe | |
| 29. |
For flow through a horizontal pipe, the pressure gradient dp/dx in the flow direction is |
| A. | +ve |
| B. | 1 |
| C. | Zero |
| D. | –ve |
| Answer» E. | |
| 30. |
A pipe of 324 mm diameter, having fiction coefficient as 0.04, connects two reservoirs with 15 m difference in their water levels through a 1500 m long pipe. What will be the discharge through the pipe? |
| A. | 104 Ips |
| B. | 134 Ips |
| C. | 165 Ips |
| D. | 196 Ips |
| Answer» B. 134 Ips | |
| 31. |
A pipe is said to be siphon if |
| A. | it can operate without external powers |
| B. | it has sub atmospheric pressure in it |
| C. | it can discharge a liquid at a fast rate |
| D. | the exit is at a lower than the inlet |
| Answer» C. it can discharge a liquid at a fast rate | |
| 32. |
Hydraulic grade line as compared to the centre line of conduit ______. |
| A. | Should be always above |
| B. | Should be always below |
| C. | Should always be parallel |
| D. | May be above or below |
| Answer» B. Should be always below | |
| 33. |
If f' is frictional resistance per unit wetted area per unit velocity and p is density of fluid then Chezy's constant is given by : |
| A. | \(C = \sqrt {\frac{{f'}}{{\rho g}}} \) |
| B. | \(C = \sqrt {\frac{{\rho g}}{{f'}}} \) |
| C. | \(C = \sqrt {\frac{{\rho }}{{f'}}} \) |
| D. | \(C = \sqrt {\frac{{f'}}{{\rho }}} \) |
| Answer» C. \(C = \sqrt {\frac{{\rho }}{{f'}}} \) | |
| 34. |
A 2 km long pipe of 0.2 m diameter connects two reservoirs. The difference between water levels in the reservoirs is 8 m. The Darcy-Weisbach friction factor of the pipe is 0.04. Accounting forfrictional, entry and exit losses, the velocity in the pipe (in m/s) is: |
| A. | 0.63 |
| B. | 0.35 |
| C. | 2.52 |
| D. | 1.25 |
| Answer» B. 0.35 | |
| 35. |
A liquid of specific weight (ρg) = 9000 N/m3 flow by gravity from a tank of 0.3 m height through a 1.2 mm diameter capillary tube at a rate of 0.004 m3/hr as shown in the figure. Sections 1 and 2 are at atmospheric pressure. Neglecting entrance effects and friction in the large tank, compute the viscosity of the liquid. Assume kinetic energy correction factor α = 2.0. |
| A. | 8.9 × 10-4 kg / m-s |
| B. | 10 × 10-4 kg / m-s |
| C. | 6.9 × 10-4 kg / m-s |
| D. | 3 × 10-4 kg / m-s |
| Answer» D. 3 × 10-4 kg / m-s | |
| 36. |
Head loss in a flowing fluid is experienced due to _____.A. Friction at surfaceB. Change of directionC. Change of section of the passageD. Obstruction in passage |
| A. | Only A |
| B. | Only B |
| C. | Only B and C |
| D. | A, B, C and D |
| Answer» E. | |
| 37. |
Due to aging of a pipe line, its carrying capacity has decreased by 25%. The corresponding increase in the Darcy weisbach friction factor f is % |
| A. | 63% |
| B. | 77% |
| C. | 56% |
| D. | None of the above |
| Answer» C. 56% | |
| 38. |
A laser Doppler anemometer is a device used to measure |
| A. | The turbulent velocity fluctuations in a flow |
| B. | Shear stress at a boundary |
| C. | Drag force on an aerofoil |
| D. | Surface tension of a fluid |
| E. | Wind direction |
| Answer» B. Shear stress at a boundary | |
| 39. |
If the fluid is ideal as per assumptions of Bernoulli’s theorem, it means that: |
| A. | Velocity is zero |
| B. | Viscosity is zero |
| C. | Flow is constant |
| D. | Pressure is constant |
| Answer» C. Flow is constant | |
| 40. |
If V is the mean velocity of flow, then according to Darcy-Weisbach equation for pipe flow energy loss over a length of pipeline is proportional to |
| A. | V |
| B. | 1/V |
| C. | 1/V2 |
| D. | V2 |
| Answer» E. | |
| 41. |
A pipe of 100 mm diameter is suddenly stretched to a diameter of 200 mm. If the discharge is 60 L/s, then calculate the loss of energy per unit weight of water. |
| A. | 2.0 m |
| B. | 3.2 m |
| C. | 1.5 m |
| D. | 1.67 m |
| Answer» E. | |
| 42. |
For laminar flow in a pipe, average velocity is equal to: |
| A. | 2 Umax |
| B. | Umax |
| C. | 0.5 Umax |
| D. | 0.25 Umax |
| Answer» D. 0.25 Umax | |
| 43. |
Match List I with List II List I List II(A)The flow is turbulent in pipes(1)Reynold number less than 2000(B)Proportional to the mean velocity(2)Loss of pressure head in laminar flow(C)The flow is laminar in pipes(3)Reynold number is more than 4000(D)Proportional to square of velocity(4)Loss of pressure head in turbulent flow |
| A. | A – 1, B – 2, C – 3, D – 4 |
| B. | A – 3, B – 2, C – 4, D – 1 |
| C. | A – 3, B – 2, C – 1, D – 4 |
| D. | A – 1, B – 4, C – 3, D – 2 |
| Answer» D. A – 1, B – 4, C – 3, D – 2 | |
| 44. |
Consider the following statements regarding anchorage of pipelines conveying water :1. At bends, pipes tend to pull apart2. At bends, forces exerted on the joints due to longitudinal shearing stresses are enormous and the joints may get loosened3. To avoid problems by hydrodynamic effects, pipes are anchored using concrete blocks which absorb side thrusts at bends4. Pipes are also anchored on steep slopesWhich of the above statements are correct? |
| A. | 1, 2 and 3 only |
| B. | 1, 2 and 4 only |
| C. | 1, 3 and 4 only |
| D. | 1, 2, 3 and 4 |
| Answer» E. | |
| 45. |
For laminar flow through a round pipe, which statement is correct? |
| A. | High velocity and high density fluid |
| B. | High velocity and high viscosity fluid |
| C. | Low velocity and high viscosity fluid |
| D. | Low density and low viscosity fluid |
| Answer» D. Low density and low viscosity fluid | |
| 46. |
A fluid of mass density 1790 kg/m3 and viscosity 2.1 Ns/m2 flows at a velocity of 3 m/s in a 6 cm diameter pipe. The head loss over a length of 12 m pipe will be nearly |
| A. | 62.0 m |
| B. | 54.0 m |
| C. | 46.5 m |
| D. | 38.5 m |
| Answer» E. | |
| 47. |
A pipe, having a length 200 m and 200 mm diameter with friction factor 0.015, is to be replaced by a 400 mm diameter pipe of friction factor 0.012 to convey the same quantity of flow. The equivalent length of the new pipe for the same head loss will be |
| A. | 8300 m |
| B. | 8240 m |
| C. | 8110 m |
| D. | 8000 m |
| Answer» E. | |
| 48. |
Net head provided by the liquid pump is given by [where, EGL = Energy grade line, HGL = hydraulic grade line, out = outlet of pump, in = Inlet of pump] |
| A. | (EGL)out + (EGL)in |
| B. | (HGL)out + (HGL)in |
| C. | (EGL)out – (EGL)in |
| D. | (HGL)out – (HGL)in |
| Answer» D. (HGL)out – (HGL)in | |
| 49. |
Darcy - Weisabach equation for loss of head in pipe is: -Where f = friction factor, L = length, V = velocitym = A/P = area/wetted perimeter |
| A. | f (L/4m).(V2/2g) |
| B. | f (L/m)(V2/2g) |
| C. | f (4L/m)(V2/2g) |
| D. | f (4m/L)(V2/2g) |
| Answer» B. f (L/m)(V2/2g) | |
| 50. |
Consider fully developed flow in a circular pipe with negligible entrance length effects. Assuming the mass flow rate, density and friction factor to be constant, if the length of the pipe is doubled and the diameter is halved, the head loss due to friction will increase by a factor of |
| A. | 4 |
| B. | 16 |
| C. | 32 |
| D. | 64 |
| Answer» E. | |