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MCQOPTIONS
This section includes 238 Mcqs, each offering curated multiple-choice questions to sharpen your Fluid Mechanics knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
Consider the following statements with regard to hydraulic turbines:1) Kaplan turbines are most efficient at part load operation.2) If n is the number of jets in a Pelton turbine, then the specific speed is proportional to n23) The flow ratio of Francis turbines are in the range of 0.1 – 0.3Which of the above statements is/are correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» D. 2 and 3 only | |
| 102. |
In a steam turbine, the nozzle angle at the inlet is 18°. The relative velocity is reduced to the extent of 6 % when steam flows over the moving blades. The output of the turbine is 120 kJ/kg flow of steam. If the blades are equiangular, the speed ratio and the absolute velocity of steam at inlet for maximum utilization are nearly |
| A. | 0.42 and 230.2 m/s |
| B. | 0.48 and 230.2 m/s |
| C. | 0.42 and 515.1 m/s |
| D. | 0.48 and 515.1 m/s |
| Answer» E. | |
| 103. |
A draft tube is used in a reaction turbine; |
| A. | To guide water downstream without splashing |
| B. | To convert residual pressure energy into kinetic energy |
| C. | To convert residual kinetic energy into pressure energy |
| D. | To streamline the flow in the tailrace |
| Answer» D. To streamline the flow in the tailrace | |
| 104. |
A Pelton wheel with a single jet rotates at 300 rpm. The velocity of the jet from the nozzle is 100 m/s. If the ratio of the vane velocity to jet velocity is 0.44, what is the diameter of the Pelton wheel? |
| A. | 2.8 m |
| B. | 1.4 m |
| C. | 0.7 m |
| D. | 2.1 m |
| Answer» B. 1.4 m | |
| 105. |
Consider the following statements:1) The wheel can be operated freely in air2) Pressure at the exit of the nozzle is atmospheric3) Pressure does not vary along the moving vanes4) Change in direction of momentum imparts thrust over moving vanesWhich of the above statements are applied to impulse turbine? |
| A. | 1, 2 and 3 only |
| B. | 1, 2 and 4 only |
| C. | 3 and 4 only |
| D. | 1, 2, 3 and 4 |
| Answer» E. | |
| 106. |
For a non-dimensional specific speed value of 1, for maximum efficiency, which of the following turbines is preferred? |
| A. | Pelton wheel |
| B. | Francis turbine |
| C. | Kaplan turbine |
| D. | Tyson wheel |
| Answer» C. Kaplan turbine | |
| 107. |
In a centrifugal pump, the flow enters the chamber along the axis of the chamber and is discharged: |
| A. | Radially |
| B. | Axially |
| C. | At a certain angle |
| D. | None of these |
| Answer» B. Axially | |
| 108. |
A Pelton wheel works under a head of 400 m. Friction loss through the pipe flow is limited to 10%. The coefficient of velocity for the jet is 0.98. What is the velocity of the jet’? Take g = 10 m/s2. |
| A. | 83 m/s |
| B. | 71 m/s |
| C. | 65 m/s |
| D. | 46 m/s |
| Answer» B. 71 m/s | |
| 109. |
If specific speed of turbine is 6, then the turbine should be |
| A. | Francis |
| B. | Kaplan |
| C. | Pelton Wheel |
| D. | Thomson |
| Answer» D. Thomson | |
| 110. |
For starting an axial flow pump, its delivery valve should be ________. |
| A. | Closed |
| B. | Open |
| C. | Depends on starting condition and flow desired |
| D. | Could be either open or closed |
| Answer» C. Depends on starting condition and flow desired | |
| 111. |
A turbine develops 500 kW power under a head of 100 in at 200 rpm. What would be its normal speed under a head of 81 m? |
| A. | 250 rpm |
| B. | 550 rpm |
| C. | 180 rpm |
| D. | 670 rpm |
| E. | 900 rpm |
| Answer» D. 670 rpm | |
| 112. |
In a centrifugal pump, discharge Q is proportional to |
| A. | N2 |
| B. | N |
| C. | N3 |
| D. | √N |
| Answer» C. N3 | |
| 113. |
Negative slip occurs in reciprocating pumps, when delivery pipe is |
| A. | Long and suction pipe is short and pump is running at low speed |
| B. | Long and suction pipe is short and pump is running at high speed |
| C. | Short and suction pipe is long and pump is running at low speed |
| D. | Short and suction pipe is long and pump is running at high speed |
| Answer» E. | |
| 114. |
A pump works on the principle of centrifugal theory, running at 900 rpm is working against a head of 16 m. The external diameter of the impeller is 360 mm and the outlet width is 40 mm. If the vane angle at the outlet is 30°and the manometric efficiency is 80%, the discharge of the pump will be: |
| A. | 0.22 m3/s |
| B. | 0.24 m3/s |
| C. | 0.18 m3/s |
| D. | 0.14 m3/s |
| Answer» E. | |
| 115. |
Cavitation in a centrifugal pump occurs when the pressure of the fluid is(Assume Pvap = Vapour pressure at working temperature of the pump) |
| A. | Less than the Pvap |
| B. | Greater than the Pvap |
| C. | Equal to the Pvap |
| D. | None of the above |
| Answer» B. Greater than the Pvap | |
| 116. |
Consider the following data relating to the performance of a centrifugal pump: speed = 1200 rpm. flow rate = 30 l/s, head = 20 m, and power = 5 kW. If the speed of the pump is increased to 1500 rpm, assuming the efficiency is unaltered, the new flow rate and head, respectively, will be |
| A. | 46.9 l/s and 25.0 m |
| B. | 37.5 l/s and 25.0 m |
| C. | 46.9 l/s and 31.3 m |
| D. | 37.5 l/s and 31.3 m |
| Answer» E. | |
| 117. |
For the maximum efficiency for the series of curved vanes, the velocity of vane is |
| A. | equal to the jet velocity |
| B. | 75% of the jet velocity |
| C. | 50% of the jet velocity |
| D. | 33% of the jet velocity |
| Answer» D. 33% of the jet velocity | |
| 118. |
Consider the following statements in respect of Kaplan turbine1. It is a reaction turbine.2. It is a mixed flow turbine.3. It has adjustable blades.Which of the statements given above are correct? |
| A. | 1, 2 and 3 |
| B. | 2 and 3 |
| C. | 1 and 3 |
| D. | 1 and 2 |
| Answer» D. 1 and 2 | |
| 119. |
In centrifugal pump, cavitation is reduced by: |
| A. | Increasing the flow velocity |
| B. | Reducing discharge |
| C. | Throttling the discharge |
| D. | Reducing suction head |
| Answer» E. | |
| 120. |
For pumps of same speed, discharge is proportional to |
| A. | Impeller diameter (D) |
| B. | D2 |
| C. | D3 |
| D. | 1/D3 |
| Answer» D. 1/D3 | |
| 121. |
A Pelton wheel is an |
| A. | Tangential flow impulse turbine |
| B. | Inward flow impulse turbine |
| C. | Outward flow impulse turbine |
| D. | Inward flow reaction turbine |
| Answer» B. Inward flow impulse turbine | |
| 122. |
If a jet of water of area ‘A’ strikes with velocity ‘V’ a series of flat plates mounted on a wheel of mean diameter D rotating at N rpm, then force exerted will be equal to |
| A. | \(\frac{{\rho A{V^2}}}{g}\) |
| B. | \(\rho AV\left( {V - \frac{{\pi DN}}{{60}}} \right)\) |
| C. | \(\frac{{\rho A}}{g} \times \frac{{\pi DN}}{{60}}\) |
| D. | \(\rho A\left( {V - \frac{{\pi DN}}{{60}}} \right)\) |
| Answer» C. \(\frac{{\rho A}}{g} \times \frac{{\pi DN}}{{60}}\) | |
| 123. |
A Pelton turbine is a/an: |
| A. | impulse flow turbine |
| B. | radial flow turbine |
| C. | mixed flow turbine |
| D. | axial flow turbine |
| Answer» B. radial flow turbine | |
| 124. |
Hydraulic pump will start pumping only when pressure head is ______ manometric head. |
| A. | equal to |
| B. | greater than |
| C. | lower than |
| D. | greater than or equal to |
| Answer» E. | |
| 125. |
For a given design of bucket, if 'u' is the velocity of the bucket and 'V1' is the velocity of the jet, then the ratio 'u/V1' for the efficiency of a Pelton wheel is theoretically maximum: |
| A. | 0.75 |
| B. | 0.25 |
| C. | 0.5 |
| D. | 1 |
| Answer» D. 1 | |
| 126. |
In an impulse reaction turbine, the enthalpy drop in fixed and moving blades are 20 kJ/Kg and 40 kJ/Kg respectively. Then the degree of reaction of stage is |
| A. | 0.33 |
| B. | 0.5 |
| C. | 0.66 |
| D. | 0.75 |
| Answer» D. 0.75 | |
| 127. |
Air vessels in reciprocating pump are used to _____. |
| A. | Smoothen flow |
| B. | Reduce acceleration to minimum |
| C. | Increase pump efficiency |
| D. | Save pump from cavitation |
| Answer» C. Increase pump efficiency | |
| 128. |
Centrifugal pumps have which of the following advantages?1. Low initial cost2. Compact, occupying less floor space3. Easy handling of highly viscous fluidsSelect the correct answer using the options given below : |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» B. 1 and 2 only | |
| 129. |
If the characteristics of a pump are as shown in figure. What is represented by abscissa? |
| A. | Head |
| B. | RPM |
| C. | Discharge |
| D. | Power |
| Answer» D. Power | |
| 130. |
In Curtis turbines |
| A. | The velocity of steam drops gradually after passing over the rows of moving blades |
| B. | The pressure of steam drops gradually after passing over the rows of moving blades |
| C. | The mass of steam drops gradually after passing over the rows of moving blades |
| D. | Both pressure and velocity of steam drops gradually after passing over the rows of moving blades |
| Answer» B. The pressure of steam drops gradually after passing over the rows of moving blades | |
| 131. |
A centrifugal pump running at 500 rpm and at its maximum efficiency is delivering a head of 30 m at a flow rate of 60 L/min. If the rpm is changed to 1000, then the head ‘H’ in meter and flow rate ‘Q’ in L/min at maximum efficiency is estimated to be |
| A. | H = 60, Q = 120 |
| B. | H = 120, Q = 120 |
| C. | H = 60, Q = 480 |
| D. | H = 120, Q = 30 |
| Answer» C. H = 60, Q = 480 | |
| 132. |
An air vessel in the delivery side of a reciprocating pump: |
| A. | maintains steady discharge output |
| B. | prevents cavitation in the system. |
| C. | enables suction head to be increased |
| D. | enable the pump to run at higher speed |
| Answer» B. prevents cavitation in the system. | |
| 133. |
For liquid being pumped, "pressure head at pump inlet + velocity head" in the suction pipe – vapor pressure head = _____ |
| A. | Stagnation head |
| B. | Net Positive Suction Head |
| C. | Total energy head |
| D. | Hydraulic head |
| Answer» C. Total energy head | |
| 134. |
_______ is a tangential - flow impulse turbine |
| A. | Pelton wheel turbine |
| B. | Kaplan turbine |
| C. | Francis turbine |
| D. | Propeller turbine |
| E. | Draft tube |
| Answer» B. Kaplan turbine | |
| 135. |
For a centrifugal pump, suction lift head is the |
| A. | Vertical distance between the top surface of liquid level in the discharged tank and pump center line |
| B. | Vertical distance between free surface of liquid level in the sump and pump center line |
| C. | Head for overcoming friction loss in the suction pipe, entry loss entrance to the friction pipe |
| D. | None of the above |
| Answer» C. Head for overcoming friction loss in the suction pipe, entry loss entrance to the friction pipe | |
| 136. |
A rocket exists exhaust gases with ρ = 0.5 kg/m3 out a 50 cm diameter nozzle at a velocity of 1200 m/s. The thrust, is |
| A. | 420 kN |
| B. | 280 kN |
| C. | 140 kN |
| D. | 90 kN |
| E. | 70 kN |
| Answer» D. 90 kN | |
| 137. |
Cconsider the following statements:1. Pumps used in series are generally of the centrifugal type.2. Centrifugal pumps, though yielding comparatively smaller discharges than axial flow pumps, yield higher heads (at each stage) compared to axial flow pumps.Which of the above statements is/are correct? |
| A. | 1 only |
| B. | 2 only |
| C. | Both 1 and 2 |
| D. | Neither 1 nor 2 |
| Answer» D. Neither 1 nor 2 | |
| 138. |
Chance of occurrence of cavitation are high if the |
| A. | Local pressure becomes very high |
| B. | Local pressure falls below the vapour pressure |
| C. | Thoma cavitation parameter exceeds a certain limit |
| D. | Local temperature becomes low |
| Answer» C. Thoma cavitation parameter exceeds a certain limit | |
| 139. |
A steam turbine in which a part of the steam after the expansion is used for process heating and the remaining steam is further expanded for power generation is/are:1.Impulse turbine2.Pass out turbine |
| A. | 1 only |
| B. | 2 only |
| C. | Both 1 and 2 |
| D. | Neither 1 nor 2 |
| Answer» C. Both 1 and 2 | |
| 140. |
A jet of water 75 mm diameter having a velocity of 20 m/s strikes normally a flat smooth plate. Determine the thrust on the plate, if the plate is at rest |
| A. | 1500 N |
| B. | 1668 N |
| C. | 1700 N |
| D. | 1768 N |
| Answer» E. | |
| 141. |
A turbine develops 500 kW under a head of 100 meters at 200 RPM. Its normal speed and power under a head of 81 meters. |
| A. | 194 RPM and 375 kW |
| B. | 180 RPM and 365 kW |
| C. | 184 RPM and 370 kW |
| D. | 180 RPM and 361 kW |
| Answer» C. 184 RPM and 370 kW | |
| 142. |
In a double acting reciprocating pump if the area of piston is 200 cm2 and length of stroke is 15 cm and crank is rotating at 60 rpm, then neglecting the losses, the discharge of pump is: |
| A. | 6 liter/min |
| B. | 60 liter/min |
| C. | 360 liter/min |
| D. | 200 liter/min |
| Answer» D. 200 liter/min | |
| 143. |
If the discharge of a centrifugal pump is throttled then its suction lift |
| A. | Decreases |
| B. | First increases and then decreases |
| C. | Remains unchanged |
| D. | Increases |
| Answer» E. | |
| 144. |
Francis turbine is |
| A. | Radial flow turbine |
| B. | Axial flow turbine |
| C. | Mixed flow turbine |
| D. | Inward flow radial turbine |
| Answer» E. | |
| 145. |
A 120 mm diameter jet of water is discharging form a nozzle into the air at a velocity of 40 m/s. The power in the jet with respect to a datum at the jet will be |
| A. | 380 kW |
| B. | 360 kW |
| C. | 340 kW |
| D. | 320 kW |
| Answer» C. 340 kW | |
| 146. |
A centrifugal pump running at 200 rpm and at its maximum efficiency is delivering a head of 30 m at a flow rate of 60 liters per min. If the speed of the pump is increased to 400 rpm, then head H is meters and flow rate Q in liters per min at maximum efficiency is |
| A. | H = 60, Q = 120 |
| B. | H = 120, Q = 120 |
| C. | H = 120, Q = 240 |
| D. | H = 60, Q = 240 |
| Answer» C. H = 120, Q = 240 | |
| 147. |
A centrifugal pump is started with its delivery valve kept |
| A. | Fully open |
| B. | Fully closed |
| C. | Partially open |
| D. | 50% open |
| Answer» C. Partially open | |
| 148. |
Cavitation is a phenomenon that occurs in turbines due to: |
| A. | formation of a boundary layer |
| B. | high viscous stress |
| C. | local vapour formation |
| D. | low viscous stress |
| Answer» D. low viscous stress | |
| 149. |
A pump speed increase, its NPSH (Net Positive Suction Head) requirement |
| A. | Increases |
| B. | Decreases |
| C. | Remains unaffected |
| D. | May increase/decrease depending on other considerations |
| Answer» E. | |
| 150. |
Hydraulic efficiency of Francis turbine whose vanes are radial at inlet is (α – guide blade angle) |
| A. | \(\frac{{2 + {{\tan }^2}\alpha }}{2}\) |
| B. | \(\frac{{{{\tan }^2}\alpha }}{2}\) |
| C. | \(\frac{2}{{2 + {{\tan }^2}\alpha }}\) |
| D. | \(\frac{2}{{ta{n^2}\alpha }}\) |
| Answer» D. \(\frac{2}{{ta{n^2}\alpha }}\) | |