Fluid Mechanics and Hydraulic Machines MCQs 2026

Torricelli theorem gives exit velocity from tank as

1. A √(gh/2) ✓
2. B 2gh without root ✓
3. C zero if orifice is sharp ✓
4. D √(2gh) ✓

Coefficient of velocity Cv for orifice is ratio of

1. A actual jet velocity to ideal velocity ✓
2. B actual discharge to ideal area velocity product ✓
3. C pressure to density ✓
4. D head loss to diameter ✓

Coefficient of contraction Cc is ratio of

1. A pipe area to orifice ✓
2. B vena contracta area to orifice area ✓
3. C velocity to discharge ✓
4. D Re to friction factor ✓

Cd for orifice equals approximately

1. A Cv times Cc ✓
2. B Cv divided by Cc ✓
3. C Cv plus Cc ✓
4. D 1 always ✓

Blower differs from compressor in that blower provides

1. A very high pressure ratio like multistage compressor ✓
2. B relatively small pressure rise at high volume flow ✓
3. C only vacuum suction ✓
4. D liquid pumping ✓

Axial flow pump is preferred when

1. A large discharge at low head is required ✓
2. B very high head low flow ✓
3. C handling highly viscous paste ✓
4. D metering precise microliters ✓

Foot valve on pump suction line prevents

1. A cavitation entirely always ✓
2. B reverse rotation of motor ✓
3. C drainage of pipe and loss of prime when pump stops ✓
4. D increase in NPSHr ✓

Priming of centrifugal pump is necessary because

1. A centrifugal pump cannot handle air and must be filled with liquid ✓
2. B it increases impeller diameter ✓
3. C it reduces NPSHa ✓
4. D it converts reciprocating to rotary motion ✓

Differential manometer connected across venturi throat and inlet measures

1. A absolute atmospheric pressure only ✓
2. B pressure difference used to calculate flow rate ✓
3. C fluid viscosity directly without formula ✓
4. D turbine shaft power ✓

Kinematic viscosity is defined as

1. A dynamic viscosity divided by density ✓
2. B density times dynamic viscosity ✓
3. C pressure divided by velocity ✓
4. D Re times diameter ✓

For laminar flow in a circular pipe, velocity profile is

1. A parabolic with maximum at center ✓
2. B flat plug flow always ✓
3. C linear from wall to center ✓
4. D zero everywhere ✓

Turbulent flow in pipes is characterized by

1. A irregular fluctuations and mixing ✓
2. B smooth layered streamlines only ✓
3. C Re below 100 always ✓
4. D zero wall shear ✓

Darcy-Weisbach equation gives

1. A pump power directly ✓
2. B Reynolds number value ✓
3. C head loss due to friction in pipes ✓
4. D surface tension force ✓

Friction factor for smooth pipes in turbulent region can be estimated by

1. A Archimedes principle only ✓
2. B Blasius or Colebrook equation ✓
3. C Pascal law only ✓
4. D Carnot efficiency formula ✓

Moody diagram relates friction factor to

1. A Reynolds number and relative roughness ✓
2. B only pipe length ✓
3. C only fluid color ✓
4. D compressibility only ✓

Minor losses in pipe systems are caused by

1. A only straight pipe friction ✓
2. B gravity alone ✓
3. C fluid density only ✓
4. D fittings, bends, valves and sudden expansions ✓

NPSH available must exceed NPSH required to avoid

1. A laminar flow only ✓
2. B increased viscosity ✓
3. C cavitation in pumps ✓
4. D positive gauge pressure always ✓

Cavitation in pumps is indicated by

1. A silent smooth operation ✓
2. B noise, vibration and pitting of impeller ✓
3. C increased NPSHa always ✓
4. D decreased temperature only ✓

Specific speed of a centrifugal pump indicates

1. A only electrical power factor ✓
2. B type and shape suitable for given Q and H ✓
3. C oil viscosity grade ✓
4. D steam pressure only ✓

Multistage centrifugal pumps are used when

1. A only very low head large flow ✓
2. B handling pure solids only ✓
3. C vacuum generation only ✓
4. D high head is required at moderate flow ✓

Reciprocating pump delivers

1. A only low pressure large flow always ✓
2. B no pulsating flow ever ✓
3. C nearly constant volume per stroke at high pressure ✓
4. D only gases ✓

Gear pump belongs to category of

1. A dynamic radial flow pumps ✓
2. B positive displacement pumps ✓
3. C gravity pumps only ✓
4. D turbines ✓

Francis turbine is classified as

1. A pure impulse only ✓
2. B wind turbine ✓
3. C mixed-flow reaction turbine ✓
4. D reciprocating engine ✓

Kaplan turbine is suitable for

1. A very high head small flow ✓
2. B zero water availability ✓
3. C compressed air only ✓
4. D low head and large discharge ✓

Draft tube in reaction turbines serves to

1. A recover kinetic energy at outlet and maintain suction head ✓
2. B increase frictional loss only ✓
3. C heat the water ✓
4. D measure flow rate only ✓

Hydraulic grade line (HGL) represents

1. A velocity head only ✓
2. B piezometric head at each point along pipe ✓
3. C temperature profile ✓
4. D Re along pipe ✓

Energy grade line (EGL) includes

1. A only static pressure ✓
2. B only elevation ✓
3. C friction factor value ✓
4. D velocity head in addition to piezometric head ✓

Pascal law in fluid statics states

1. A pressure at a point is transmitted equally in all directions ✓
2. B pressure increases with velocity always ✓
3. C fluid always flows uphill ✓
4. D density is constant in gases only ✓

Hydrostatic pressure at depth h in liquid is

1. A ρg/h ✓
2. B h/ρg ✓
3. C ρgh ✓
4. D zero at all depths ✓

Buoyant force on submerged body equals

1. A weight of displaced fluid ✓
2. B weight of body always ✓
3. C half displaced volume only ✓
4. D surface tension force ✓

Metacentric height GM positive indicates

1. A always capsizing ✓
2. B neutral stability only ✓
3. C stable floating equilibrium ✓
4. D no restoring moment ✓

Capillary rise in small tube is due to

1. A surface tension and wetting ✓
2. B only gravity increase ✓
3. C turbulent mixing ✓
4. D compressibility ✓

Newton law of viscosity states shear stress is proportional to

1. A rate of strain (velocity gradient) ✓
2. B pressure only ✓
3. C absolute temperature only ✓
4. D density squared ✓

Non-Newtonian fluid example is

1. A blood or polymer solution ✓
2. B water at 20 °C ✓
3. C air at low speed ✓
4. D mercury ✓

Steady flow means

1. A uniform flow at all cross sections always ✓
2. B zero velocity everywhere ✓
3. C Re is constant in time only at inlet ✓
4. D properties at a point do not change with time ✓

Uniform flow in open channel implies

1. A only steady in time ✓
2. B always supercritical ✓
3. C always laminar ✓
4. D depth and velocity constant along channel length ✓

Streamline is a line

1. A tangent to velocity vector everywhere ✓
2. B perpendicular to flow always ✓
3. C along which pressure is zero ✓
4. D of constant temperature only ✓

Path line of fluid particle is

1. A always straight line ✓
2. B actual trajectory traced by that particle ✓
3. C same as streak line always in unsteady flow ✓
4. D always parallel to wall ✓

Streak line is

1. A instantaneous velocity direction only ✓
2. B constant pressure line ✓
3. C locus of particles passing through a common point ✓
4. D pipe centerline always ✓

Euler equation along streamline for inviscid flow relates

1. A shear stress to viscosity only ✓
2. B heat transfer to conductivity ✓
3. C pressure gradient to velocity and body force ✓
4. D mass to moles ✓

Navier-Stokes equations include

1. A only hydrostatic terms ✓
2. B viscous stress terms in momentum balance ✓
3. C combustion chemistry ✓
4. D electromagnetic forces only ✓

Transition from laminar to turbulent pipe flow depends on

1. A pipe material color only ✓
2. B only pipe length ✓
3. C Reynolds number and disturbances ✓
4. D absolute pressure only ✓

Hydraulic jump energy loss appears as

1. A increased mechanical energy in flow ✓
2. B stored elastic energy ✓
3. C pump head gain ✓
4. D turbulence and heat dissipation ✓

Bernoulli equation for steady incompressible flow along a streamline states that

1. A velocity head alone is constant ✓
2. B pressure always increases with height ✓
3. C total head remains constant ✓
4. D flow rate changes with pipe diameter only ✓

Continuity equation for incompressible flow in a pipe is expressed as

1. A p1 = p2 always ✓
2. B A1V1 = A2V2 ✓
3. C Q changes with viscosity ✓
4. D Re is constant everywhere ✓

Reynolds number Re is defined as

1. A μVD/ρ ✓
2. B VD/g ✓
3. C p/ρV² ✓
4. D ρVD/μ ✓

Dynamic viscosity unit in SI is

1. A m²/s only ✓
2. B Pa·s (N·s/m²) ✓
3. C N/m only ✓
4. D kg/m only ✓

Flow in a smooth pipe is generally laminar when Reynolds number is below

1. A 4000 ✓
2. B 10000 ✓
3. C 500 ✓
4. D 2300 ✓

Boundary layer thickness increases along a flat plate because

1. A pressure always decreases ✓
2. B density becomes zero ✓
3. C viscous effects diffuse momentum outward ✓
4. D Re decreases to zero ✓

Centrifugal pump imparts energy to fluid mainly by

1. A increasing kinetic energy then converting to pressure ✓
2. B heating the fluid only ✓
3. C decreasing angular momentum ✓
4. D compressing vapor ✓

Pelton wheel is an example of

1. A reaction turbine only ✓
2. B impulse turbine ✓
3. C positive displacement pump ✓
4. D reciprocating pump ✓

Hydraulic ram utilizes

1. A steam expansion only ✓
2. B water hammer effect to pump a portion of water to higher elevation ✓
3. C electromagnetic induction ✓
4. D centrifugal impeller only ✓

Simple U-tube manometer measures

1. A pressure difference as liquid column height difference ✓
2. B mass flow rate directly ✓
3. C Reynolds number ✓
4. D turbine power only ✓

Venturi meter measures flow rate based on

1. A temperature rise in throat ✓
2. B pressure difference between converging and throat sections ✓
3. C color change of fluid ✓
4. D magnetic field strength ✓

Orifice meter causes greater permanent pressure loss than venturi because

1. A it has a longer converging cone ✓
2. B it measures temperature instead ✓
3. C discharge coefficient is unity ✓
4. D no gradual recovery section after restriction ✓

Stokes law gives drag on small sphere as

1. A FD independent of viscosity ✓
2. B FD proportional to V² only ✓
3. C FD = 3πμDV ✓
4. D FD zero in viscous flow ✓

Terminal velocity of falling particle occurs when

1. A acceleration is maximum ✓
2. B Re is infinite always ✓
3. C drag force equals net weight minus buoyancy ✓
4. D viscosity is zero ✓

Pitot tube measures

1. A static pressure only in all cases ✓
2. B mass of fluid ✓
3. C stagnation pressure to find local velocity ✓
4. D turbine efficiency ✓

Coefficient of discharge for venturi is typically

1. A zero always ✓
2. B higher than for sharp-edged orifice ✓
3. C lower than orifice always ✓
4. D exactly 1.0 always ✓

Rotameter measures flow using

1. A electromagnetic induction only ✓
2. B orifice plate only ✓
3. C float equilibrium in tapered tube ✓
4. D thermocouple ✓

Weir flow measurement for rectangular sharp-crested weir varies discharge approximately as

1. A H linearly only ✓
2. B H² only ✓
3. C H^(3/2) ✓
4. D independent of head ✓

Chezy and Manning formulas estimate

1. A closed pipe laminar flow only ✓
2. B velocity or discharge in open channels ✓
3. C compressor performance ✓
4. D Rankine cycle efficiency ✓

Hydraulic radius R is defined as

1. A perimeter divided by area ✓
2. B diameter squared ✓
3. C velocity times area ✓
4. D flow area divided by wetted perimeter ✓

Froude number characterizes

1. A viscous to inertial forces only ✓
2. B Mach number in liquids ✓
3. C pump NPSH ✓
4. D relative importance of inertia to gravity in open channel flow ✓

Critical depth in rectangular channel occurs when

1. A Re equals 2300 ✓
2. B flow is always subcritical ✓
3. C Froude number equals unity ✓
4. D depth is maximum always ✓

Hydraulic jump occurs in

1. A laminar to turbulent in pipe only ✓
2. B pump suction line only ✓
3. C closed valve only ✓
4. D supercritical to subcritical transition ✓

Surface tension σ has unit

1. A Pa·s ✓
2. B N/m ✓
3. C m²/s ✓
4. D kg/m³ ✓

Vapor pressure of liquid is important in pumps because

1. A it increases pipe roughness ✓
2. B it eliminates friction loss ✓
3. C it raises NPSHa always ✓
4. D low pressure can cause boiling and cavitation ✓

Head developed by centrifugal pump for given impeller speed and diameter is independent of

1. A fluid density ✓
2. B impeller diameter ✓
3. C rotational speed ✓
4. D impeller design ✓

Affinity laws for pumps state flow rate varies with speed as

1. A Q proportional to N² ✓
2. B Q proportional to N ✓
3. C Q independent of N ✓
4. D Q proportional to 1/N ✓

System curve for pipe network intersects pump curve at

1. A shutoff head only ✓
2. B maximum efficiency always ✓
3. C zero flow always ✓
4. D operating point ✓

Water hammer pressure surge depends on

1. A only pipe color ✓
2. B only ambient temperature ✓
3. C Re only ✓
4. D wave speed and velocity change ✓

Surge tank in hydro penstock reduces

1. A turbine efficiency to zero ✓
2. B reservoir volume ✓
3. C net head permanently ✓
4. D water hammer pressure fluctuations ✓

Impulse turbine runner operates in

1. A high vacuum only inside blades always ✓
2. B pressurized sealed casing only ✓
3. C atmospheric pressure region ✓
4. D oil bath ✓

Degree of reaction for turbine is ratio of

1. A enthalpy drop in rotor to total enthalpy drop ✓
2. B power to speed ✓
3. C inlet to outlet pressure only ✓
4. D torque to angular velocity only ✓

Cavitation parameter σ for turbines relates to

1. A only steam quality ✓
2. B NPSH and net head ✓
3. C fuel air ratio ✓
4. D COP of refrigerator ✓

Hydraulic efficiency of turbine is

1. A water power output divided by energy supplied in flow ✓
2. B electrical output only without losses ✓
3. C volumetric efficiency of pump ✓
4. D boiler efficiency ✓

Inverted U-tube manometer is used for

1. A high vacuum in steam condenser only always ✓
2. B liquid flow in open channel only ✓
3. C measuring torque ✓
4. D measuring small pressure differences in gases ✓

Barometer measures

1. A gauge pressure in pipe always ✓
2. B dynamic pressure only ✓
3. C local atmospheric pressure ✓
4. D mass flow rate ✓

Gauge pressure equals

1. A absolute plus atmospheric ✓
2. B vacuum pressure always ✓
3. C twice absolute pressure ✓
4. D absolute pressure minus atmospheric pressure ✓