Fluid Mechanics and Hydraulics MCQs 2026

The centre of buoyancy of a submerged body is the centroid of

1. Abody mass✓
2. Bwater surface area✓
3. Cpressure diagram on atmosphere✓
4. Ddisplaced fluid volume✓

For a fully submerged body, stable equilibrium requires

1. Acentre of gravity below centre of buoyancy✓
2. BCG above CB✓
3. CCG coincident with free surface✓
4. Dneutral metacentre at infinity✓

In fluid flow, a streamline is a line

1. Aof constant pressure only✓
2. Bparallel to channel bed only✓
3. Cof zero shear stress✓
4. Dtangent to velocity vector at every point✓

Steady flow means at a fixed point

1. Aflow properties do not change with time✓
2. Bvelocity is zero everywhere✓
3. Cpressure is uniform in field✓
4. DReynolds number is constant globally✓

Uniform flow in an open channel has

1. Avarying depth along length✓
2. Bdepth and velocity constant along the channel reach✓
3. Czero discharge✓
4. Dalways supercritical flow✓

Turbulent flow is characterised by

1. Arandom fluctuating velocity components and mixing✓
2. Bsmooth layered motion only✓
3. CReynolds number below 1✓
4. Dzero wall shear✓

Continuity equation for incompressible steady flow is

1. AP + ρgh = constant always✓
2. Bτ = μ du/dy✓
3. Ch_f = fLV²/(2gD)✓
4. DQ = AV = constant✓

Bernoulli equation along a streamline for ideal flow states

1. Ap = ρgh only✓
2. BV = constant always✓
3. Cp/ρg + V²/(2g) + z = constant✓
4. DfL/D = constant✓

Application of Bernoulli between two points requires

1. Aturbulent mixing always allowed✓
2. Bcompressible supersonic flow always✓
3. Cunsteady pulsating flow✓
4. Dsteady, inviscid, incompressible flow along streamline✓

Velocity head is expressed as

1. AV²/(2g)✓
2. BV/g✓
3. C2g/V²✓
4. DρV²✓

Piezometric head at a point equals

1. Ap/(ρg) + z✓
2. BV²/(2g) only✓
3. Cp/(ρg) only✓
4. Dz − p/(ρg)✓

Total energy head H in open channel flow is

1. Ay only✓
2. BV²/(2g) only✓
3. Cz − y✓
4. Dz + y + V²/(2g) for datum at bed✓

Venturi meter measures flow rate using

1. Atemperature change only✓
2. Bmagnetic induction✓
3. CManning equation✓
4. Dpressure difference between converging and throat sections✓

Pitot tube measures

1. Adynamic viscosity✓
2. Bstagnation pressure to obtain velocity✓
3. CManning roughness✓
4. Dsediment concentration✓

Orifice meter causes permanent pressure loss because of

1. ABernoulli being invalid✓
2. Bzero velocity at throat✓
3. Ccontraction and turbulence at the orifice✓
4. Dlaminar flow requirement✓

Momentum equation in fluid mechanics is based on

1. Afirst law of thermodynamics only✓
2. BFick law of diffusion✓
3. CNewton second law for control volume✓
4. DDarcy law for porous media✓

Force exerted by a jet on a flat plate is

1. A½ρAV² only always✓
2. BρgAH✓
3. CρAV² for normal impact when plate is stationary✓
4. Dzero for any angle✓

When a jet strikes a curved vane and deflects through angle θ, force component depends on

1. Aonly weight of vane✓
2. Bchange in momentum in flow direction✓
3. CManning n✓
4. DReynolds number alone✓

Hydraulic jump occurs in open channel when

1. Asubcritical becomes laminar pipe flow✓
2. Bflow becomes uniform always✓
3. Csupercritical flow transitions to subcritical flow✓
4. Ddepth remains constant✓

Specific force in open channel momentum analysis is

1. AQ/A only✓
2. BQ²/(gA) + Aȳ✓
3. CV²/(2g)✓
4. DManning V✓

Impulse-momentum principle is preferred over Bernoulli when calculating

1. Astatic pressure at a point only✓
2. Bforces on bends, reducers and structures✓
3. Ccapillary rise✓
4. Dvapour pressure✓

Reynolds number Re is defined as

1. AρVD/μ or VD/ν✓
2. BμVD/ρ✓
3. CρgD/μ✓
4. DV²D/g✓

For pipe flow, critical Reynolds number for transition to turbulence is approximately

1. A100✓
2. B50000✓
3. C10✓
4. D2300✓

Laminar pipe flow velocity profile is

1. Auniform plug flow✓
2. Blinear from wall to centre✓
3. Czero at centre✓
4. Dparabolic with maximum at centre✓

In laminar flow through circular pipe, head loss varies with velocity as

1. AV✓
2. BV²✓
3. CV³✓
4. Dindependent of V✓

Hydraulic radius R for full circular pipe equals

1. AD/2✓
2. BD/4✓
3. CπD²/4✓
4. DD✓

Draft tube in reaction turbine serves to

1. Aincrease atmospheric pressure✓
2. Bmeasure discharge✓
3. Cfilter sediment✓
4. Drecover kinetic energy and maintain suction head at runner✓

Discharge over a rectangular sharp-crested weir is proportional to

1. AH only✓
2. BH^(3/2)✓
3. CH²✓
4. D√H for all weir types✓

V-notch weir is preferred for measuring

1. Avery high floods only✓
2. Bgroundwater seepage directly✓
3. Clow discharges with better sensitivity✓
4. Dpipe pressure only✓

Coefficient of discharge for orifice is less than unity due to

1. Agravity variation✓
2. BManning n in pipe✓
3. Ccontraction and energy losses✓
4. DCoriolis effect✓

Torricelli theorem gives jet velocity from orifice as

1. Agh only✓
2. B√(2gh)✓
3. C2gh without root✓
4. D√(gh/2)✓

Buckingham Pi theorem states that a problem with n variables and k fundamental dimensions has

1. An − k independent dimensionless groups✓
2. Bn + k groups✓
3. Ck − n groups✓
4. Dalways one group✓

Reynolds number is a dimensionless group representing ratio of

1. Agravity to viscosity✓
2. Bpressure to shear only✓
3. Csurface tension to gravity only✓
4. Dinertial forces to viscous forces✓

Froude number similarity is essential in modeling

1. Afree-surface gravity-driven flows✓
2. Bcreeping laminar pipe flow only✓
3. CDarcy groundwater flow✓
4. Dpure diffusion✓

Geometric, kinematic and dynamic similarities together ensure

1. Aonly same colour of fluid✓
2. Bcomplete model-prototype similitude for intended laws✓
3. Conly same pipe material✓
4. Donly same temperature✓

Surface tension in a liquid is caused by

1. Agravitational pull only✓
2. Bviscous shear at walls✓
3. CBernoulli pressure drop✓
4. Dcohesive forces at the free surface✓

Dynamic viscosity of a fluid is defined as the ratio of

1. Adensity to velocity✓
2. Bshear stress to rate of shear strain✓
3. Cpressure to temperature✓
4. Dvelocity to area✓

Kinematic viscosity ν is related to dynamic viscosity μ by

1. Aν = μρ✓
2. Bν = ρ/μ²✓
3. Cν = μ + ρ✓
4. Dν = μ/ρ✓

The bulk modulus of elasticity of a liquid measures

1. Asurface tension effects only✓
2. Bresistance to uniform compression✓
3. Cshear deformation only✓
4. Dturbulent mixing rate✓

Vapour pressure of water increases with

1. Adepth in a reservoir only✓
2. Bpipe diameter only✓
3. Cchannel slope only✓
4. Dtemperature✓

A Newtonian fluid is one in which

1. Aviscosity changes with time always✓
2. Bshear stress is directly proportional to velocity gradient✓
3. Cdensity is constant only in gases✓
4. DReynolds number exceeds 4000✓

Specific weight γ of a fluid equals

1. Aρ/g✓
2. Bμρ✓
3. Cρg✓
4. Dρ + g✓

Compressibility of water is generally considered negligible in

1. Apipe flow and open channel problems at low Mach number✓
2. Bcavitation analysis always✓
3. Cwater hammer studies✓
4. Dhigh-speed jet flows✓

Hydrostatic pressure at a point in a static fluid depends on

1. Adepth, fluid density and gravitational acceleration✓
2. Bflow velocity only✓
3. Cpipe roughness only✓
4. DReynolds number✓

Pascal law states that pressure applied to a confined fluid

1. Ais transmitted undiminished in all directions✓
2. Bacts only vertically downward✓
3. Cdecreases with depth always✓
4. Ddepends on container shape for intensity✓

The centre of pressure on a submerged plane surface is

1. Aabove the centroid always✓
2. Bcoincident with centroid always✓
3. Cat the water surface✓
4. Dbelow the centroid because pressure increases with depth✓

Total hydrostatic force on a vertical plane surface equals

1. AγA only✓
2. B½γH² only without area✓
3. Cvelocity head times area✓
4. Dγh̄A where h̄ is depth to centroid✓

Pressure head in fluid mechanics is expressed as

1. Ap/(ρg)✓
2. Bρgp✓
3. Cpρg✓
4. Dp + ρg✓

Absolute pressure equals gauge pressure plus

1. Avacuum pressure only✓
2. Batmospheric pressure✓
3. Cvelocity head✓
4. Dvapour pressure always✓

A manometer reading measures

1. Aflow rate directly✓
2. BReynolds number✓
3. Cdifference in pressure between two points or from atmosphere✓
4. DManning n directly✓

Hydrostatic paradox demonstrates that

1. Apressure depends on container shape at same depth✓
2. Bdeeper vessels always have lower pressure✓
3. Cforce on container bottom depends on depth and area, not total water volume shape✓
4. Dhorizontal forces are always zero✓

Archimedes principle states buoyant force equals

1. Aweight of the body in air✓
2. Bweight of fluid displaced by the body✓
3. Chalf the submerged volume only✓
4. Dsurface tension force✓

A body floats when its average specific gravity is

1. Aequal to zero only✓
2. Bgreater than 2.0 always✓
3. Cless than that of the fluid✓
4. Dequal to fluid SG with no submergence✓

Metacentric height GM is positive when a floating body is

1. Aunstable and capsizing✓
2. Bstable in small angular disturbances✓
3. Cneutrally buoyant only✓
4. Dfully submerged always✓

Darcy-Weisbach head loss formula is

1. Ah_f = n²V²R^(4/3)✓
2. Bh_f = f (L/D)(V²/2g)✓
3. Ch_f = KL²✓
4. Dh_f = μV only✓

Hazen-Williams formula is primarily used for

1. Awater distribution pipes in turbulent regime✓
2. Blaminar laboratory tubes only✓
3. Copen channel Manning alternative only✓
4. Dcompressible gas pipelines✓

Moody diagram relates friction factor f to

1. AFroude number only✓
2. BManning n only✓
3. Cweir crest length✓
4. DReynolds number and relative roughness✓

Colebrook-White equation is used to find

1. ADarcy friction factor in turbulent pipe flow✓
2. BManning n from grain size✓
3. Ccritical depth directly✓
4. Dpump NPSH✓

Minor losses in pipe systems are expressed as

1. AK V²/(2g)✓
2. BfL/D only✓
3. CManning S✓
4. DρgH pump head✓

Velocity in pipe for given discharge is maximum when

1. Adiameter is largest✓
2. Barea is minimum for same Q✓
3. Croughness is highest✓
4. Dpipe is horizontal✓

Parallel pipes carrying same total head loss have

1. Aequal discharge always✓
2. Binverse relationship between resistance and discharge share✓
3. Czero flow in smaller pipe✓
4. Dsame velocity regardless of diameter✓

Series pipes have

1. Asame head loss in each✓
2. Bindependent discharges✓
3. Csame discharge through each pipe section✓
4. Dzero velocity in second pipe✓

Water hammer pressure rise is proportional to

1. Achange in velocity and wave celerity✓
2. Bpipe length only✓
3. CManning n✓
4. Dchannel width only✓

Cavitation in pumps occurs when local pressure falls below

1. Aatmospheric pressure at all points✓
2. Bstagnation pressure✓
3. CManning normal depth✓
4. Dvapour pressure of the liquid✓

Manning formula for open channel velocity is

1. AV = √(gD)✓
2. BV = fL/D✓
3. CV = C√(RS) Hazen only✓
4. DV = (1/n) R^(2/3) S^(1/2)✓

Manning n increases with

1. Aflow depth decrease only✓
2. Bhigher Reynolds always decreasing n✓
3. Cchannel roughness and vegetation✓
4. Dsubcritical flow only✓

Hydraulic radius for wide rectangular channel approximates

1. Awidth b✓
2. Bb + y✓
3. Cy/2 only for all widths✓
4. Ddepth y✓

Specific energy E in open channel is

1. Ay − V²/(2g)✓
2. BQ²/(2g)✓
3. Cy + V²/(2g)✓
4. Dz + p/γ✓

Critical depth occurs when specific energy is

1. Amaximum always✓
2. Bzero✓
3. Cminimum for given discharge✓
4. Dequal to normal depth always✓

Froude number Fr is defined as

1. AV/gD✓
2. B√(gD)/V✓
3. CV/√(gD_h)✓
4. DρV²D/μ✓

Subcritical flow in open channel is controlled from

1. Aupstream only always✓
2. Bdownstream conditions✓
3. Cmid-channel only✓
4. Datmosphere only✓

Supercritical flow is controlled from

1. Aupstream✓
2. Bdownstream✓
3. Cboth ends equally always✓
4. Dneither end✓

Gradually varied flow (GVF) profiles depend on

1. Apipe friction factor only✓
2. Bpump power only✓
3. Crelation of actual depth to normal and critical depths✓
4. DBOD loading✓

Rapidly varied flow includes

1. Auniform flow in long canal✓
2. Blaminar pipe flow✓
3. CDarcy groundwater flow✓
4. Dhydraulic jump and flow over weirs✓

Centrifugal pump head is the energy imparted per unit

1. Avolume only✓
2. Bweight of liquid✓
3. Cmass times g only without head concept✓
4. Dtime only✓

NPSH available must exceed NPSH required to avoid

1. Acavitation at pump suction✓
2. Bwater hammer in delivery pipe✓
3. CManning depth error✓
4. Dsediment deposition✓

Specific speed N_s of a pump indicates

1. Aonly motor RPM✓
2. Bpipe diameter only✓
3. Ctype and suitability for head-discharge duty✓
4. DManning roughness✓

Characteristic curves of centrifugal pump relate

1. Aonly pipe friction factor✓
2. Bonly channel slope✓
3. Chead, power and efficiency to discharge✓
4. Donly rainfall intensity✓

Pelton turbine is best suited for

1. Alow head high flow rivers✓
2. Btidal barrages only✓
3. Chigh head and low discharge✓
4. Ddrainage pumps✓

Francis turbine is a

1. Amixed-flow reaction turbine for medium head✓
2. Bpure impulse axial only✓
3. Cpositive displacement pump✓
4. Dtrickling filter✓