Fluid Mechanics and Hydraulics MCQs 2026

Dynamic viscosity of a fluid is defined as the ratio of

1. A density to velocity ✓
2. B shear stress to rate of shear strain ✓
3. C pressure to temperature ✓
4. D velocity to area ✓

Kinematic viscosity ν is related to dynamic viscosity μ by

1. A ν = μρ ✓
2. B ν = ρ/μ² ✓
3. C ν = μ + ρ ✓
4. D ν = μ/ρ ✓

The bulk modulus of elasticity of a liquid measures

1. A surface tension effects only ✓
2. B resistance to uniform compression ✓
3. C shear deformation only ✓
4. D turbulent mixing rate ✓

Surface tension in a liquid is caused by

1. A gravitational pull only ✓
2. B viscous shear at walls ✓
3. C Bernoulli pressure drop ✓
4. D cohesive forces at the free surface ✓

Vapour pressure of water increases with

1. A depth in a reservoir only ✓
2. B pipe diameter only ✓
3. C channel slope only ✓
4. D temperature ✓

A Newtonian fluid is one in which

1. A viscosity changes with time always ✓
2. B shear stress is directly proportional to velocity gradient ✓
3. C density is constant only in gases ✓
4. D Reynolds number exceeds 4000 ✓

Specific weight γ of a fluid equals

1. A ρ/g ✓
2. B μρ ✓
3. C ρg ✓
4. D ρ + g ✓

Compressibility of water is generally considered negligible in

1. A pipe flow and open channel problems at low Mach number ✓
2. B cavitation analysis always ✓
3. C water hammer studies ✓
4. D high-speed jet flows ✓

Hydrostatic pressure at a point in a static fluid depends on

1. A depth, fluid density and gravitational acceleration ✓
2. B flow velocity only ✓
3. C pipe roughness only ✓
4. D Reynolds number ✓

Pascal law states that pressure applied to a confined fluid

1. A is transmitted undiminished in all directions ✓
2. B acts only vertically downward ✓
3. C decreases with depth always ✓
4. D depends on container shape for intensity ✓

The centre of pressure on a submerged plane surface is

1. A above the centroid always ✓
2. B coincident with centroid always ✓
3. C at the water surface ✓
4. D below the centroid because pressure increases with depth ✓

Total hydrostatic force on a vertical plane surface equals

1. A γA only ✓
2. B ½γH² only without area ✓
3. C velocity head times area ✓
4. D γh̄A where h̄ is depth to centroid ✓

Pressure head in fluid mechanics is expressed as

1. A p/(ρg) ✓
2. B ρgp ✓
3. C pρg ✓
4. D p + ρg ✓

Absolute pressure equals gauge pressure plus

1. A vacuum pressure only ✓
2. B atmospheric pressure ✓
3. C velocity head ✓
4. D vapour pressure always ✓

A manometer reading measures

1. A flow rate directly ✓
2. B Reynolds number ✓
3. C difference in pressure between two points or from atmosphere ✓
4. D Manning n directly ✓

Hydrostatic paradox demonstrates that

1. A pressure depends on container shape at same depth ✓
2. B deeper vessels always have lower pressure ✓
3. C force on container bottom depends on depth and area, not total water volume shape ✓
4. D horizontal forces are always zero ✓

Archimedes principle states buoyant force equals

1. A weight of the body in air ✓
2. B weight of fluid displaced by the body ✓
3. C half the submerged volume only ✓
4. D surface tension force ✓

A body floats when its average specific gravity is

1. A equal to zero only ✓
2. B greater than 2.0 always ✓
3. C less than that of the fluid ✓
4. D equal to fluid SG with no submergence ✓

Metacentric height GM is positive when a floating body is

1. A unstable and capsizing ✓
2. B stable in small angular disturbances ✓
3. C neutrally buoyant only ✓
4. D fully submerged always ✓

Darcy-Weisbach head loss formula is

1. A h_f = n²V²R^(4/3) ✓
2. B h_f = f (L/D)(V²/2g) ✓
3. C h_f = KL² ✓
4. D h_f = μV only ✓

Hazen-Williams formula is primarily used for

1. A water distribution pipes in turbulent regime ✓
2. B laminar laboratory tubes only ✓
3. C open channel Manning alternative only ✓
4. D compressible gas pipelines ✓

Moody diagram relates friction factor f to

1. A Froude number only ✓
2. B Manning n only ✓
3. C weir crest length ✓
4. D Reynolds number and relative roughness ✓

Colebrook-White equation is used to find

1. A Darcy friction factor in turbulent pipe flow ✓
2. B Manning n from grain size ✓
3. C critical depth directly ✓
4. D pump NPSH ✓

Minor losses in pipe systems are expressed as

1. A K V²/(2g) ✓
2. B fL/D only ✓
3. C Manning S ✓
4. D ρgH pump head ✓

Velocity in pipe for given discharge is maximum when

1. A diameter is largest ✓
2. B area is minimum for same Q ✓
3. C roughness is highest ✓
4. D pipe is horizontal ✓

Parallel pipes carrying same total head loss have

1. A equal discharge always ✓
2. B inverse relationship between resistance and discharge share ✓
3. C zero flow in smaller pipe ✓
4. D same velocity regardless of diameter ✓

Series pipes have

1. A same head loss in each ✓
2. B independent discharges ✓
3. C same discharge through each pipe section ✓
4. D zero velocity in second pipe ✓

Water hammer pressure rise is proportional to

1. A change in velocity and wave celerity ✓
2. B pipe length only ✓
3. C Manning n ✓
4. D channel width only ✓

Cavitation in pumps occurs when local pressure falls below

1. A atmospheric pressure at all points ✓
2. B stagnation pressure ✓
3. C Manning normal depth ✓
4. D vapour pressure of the liquid ✓

Manning formula for open channel velocity is

1. A V = √(gD) ✓
2. B V = fL/D ✓
3. C V = C√(RS) Hazen only ✓
4. D V = (1/n) R^(2/3) S^(1/2) ✓

Manning n increases with

1. A flow depth decrease only ✓
2. B higher Reynolds always decreasing n ✓
3. C channel roughness and vegetation ✓
4. D subcritical flow only ✓

Hydraulic radius for wide rectangular channel approximates

1. A width b ✓
2. B b + y ✓
3. C y/2 only for all widths ✓
4. D depth y ✓

Specific energy E in open channel is

1. A y − V²/(2g) ✓
2. B Q²/(2g) ✓
3. C y + V²/(2g) ✓
4. D z + p/γ ✓

Critical depth occurs when specific energy is

1. A maximum always ✓
2. B zero ✓
3. C minimum for given discharge ✓
4. D equal to normal depth always ✓

Froude number Fr is defined as

1. A V/gD ✓
2. B √(gD)/V ✓
3. C V/√(gD_h) ✓
4. D ρV²D/μ ✓

Subcritical flow in open channel is controlled from

1. A upstream only always ✓
2. B downstream conditions ✓
3. C mid-channel only ✓
4. D atmosphere only ✓

Supercritical flow is controlled from

1. A upstream ✓
2. B downstream ✓
3. C both ends equally always ✓
4. D neither end ✓

Gradually varied flow (GVF) profiles depend on

1. A pipe friction factor only ✓
2. B pump power only ✓
3. C relation of actual depth to normal and critical depths ✓
4. D BOD loading ✓

Rapidly varied flow includes

1. A uniform flow in long canal ✓
2. B laminar pipe flow ✓
3. C Darcy groundwater flow ✓
4. D hydraulic jump and flow over weirs ✓

Centrifugal pump head is the energy imparted per unit

1. A volume only ✓
2. B weight of liquid ✓
3. C mass times g only without head concept ✓
4. D time only ✓

NPSH available must exceed NPSH required to avoid

1. A cavitation at pump suction ✓
2. B water hammer in delivery pipe ✓
3. C Manning depth error ✓
4. D sediment deposition ✓

Specific speed N_s of a pump indicates

1. A only motor RPM ✓
2. B pipe diameter only ✓
3. C type and suitability for head-discharge duty ✓
4. D Manning roughness ✓

Characteristic curves of centrifugal pump relate

1. A only pipe friction factor ✓
2. B only channel slope ✓
3. C head, power and efficiency to discharge ✓
4. D only rainfall intensity ✓

Pelton turbine is best suited for

1. A low head high flow rivers ✓
2. B tidal barrages only ✓
3. C high head and low discharge ✓
4. D drainage pumps ✓

Francis turbine is a

1. A mixed-flow reaction turbine for medium head ✓
2. B pure impulse axial only ✓
3. C positive displacement pump ✓
4. D trickling filter ✓

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

1. A body mass ✓
2. B water surface area ✓
3. C pressure diagram on atmosphere ✓
4. D displaced fluid volume ✓

For a fully submerged body, stable equilibrium requires

1. A centre of gravity below centre of buoyancy ✓
2. B CG above CB ✓
3. C CG coincident with free surface ✓
4. D neutral metacentre at infinity ✓

In fluid flow, a streamline is a line

1. A of constant pressure only ✓
2. B parallel to channel bed only ✓
3. C of zero shear stress ✓
4. D tangent to velocity vector at every point ✓

Steady flow means at a fixed point

1. A flow properties do not change with time ✓
2. B velocity is zero everywhere ✓
3. C pressure is uniform in field ✓
4. D Reynolds number is constant globally ✓

Uniform flow in an open channel has

1. A varying depth along length ✓
2. B depth and velocity constant along the channel reach ✓
3. C zero discharge ✓
4. D always supercritical flow ✓

Turbulent flow is characterised by

1. A random fluctuating velocity components and mixing ✓
2. B smooth layered motion only ✓
3. C Reynolds number below 1 ✓
4. D zero wall shear ✓

Continuity equation for incompressible steady flow is

1. A P + ρgh = constant always ✓
2. B τ = μ du/dy ✓
3. C h_f = fLV²/(2gD) ✓
4. D Q = AV = constant ✓

Bernoulli equation along a streamline for ideal flow states

1. A p = ρgh only ✓
2. B V = constant always ✓
3. C p/ρg + V²/(2g) + z = constant ✓
4. D fL/D = constant ✓

Application of Bernoulli between two points requires

1. A turbulent mixing always allowed ✓
2. B compressible supersonic flow always ✓
3. C unsteady pulsating flow ✓
4. D steady, inviscid, incompressible flow along streamline ✓

Velocity head is expressed as

1. A V²/(2g) ✓
2. B V/g ✓
3. C 2g/V² ✓
4. D ρV² ✓

Piezometric head at a point equals

1. A p/(ρg) + z ✓
2. B V²/(2g) only ✓
3. C p/(ρg) only ✓
4. D z − p/(ρg) ✓

Total energy head H in open channel flow is

1. A y only ✓
2. B V²/(2g) only ✓
3. C z − y ✓
4. D z + y + V²/(2g) for datum at bed ✓

Venturi meter measures flow rate using

1. A temperature change only ✓
2. B magnetic induction ✓
3. C Manning equation ✓
4. D pressure difference between converging and throat sections ✓

Pitot tube measures

1. A dynamic viscosity ✓
2. B stagnation pressure to obtain velocity ✓
3. C Manning roughness ✓
4. D sediment concentration ✓

Orifice meter causes permanent pressure loss because of

1. A Bernoulli being invalid ✓
2. B zero velocity at throat ✓
3. C contraction and turbulence at the orifice ✓
4. D laminar flow requirement ✓

Momentum equation in fluid mechanics is based on

1. A first law of thermodynamics only ✓
2. B Fick law of diffusion ✓
3. C Newton second law for control volume ✓
4. D Darcy law for porous media ✓

Force exerted by a jet on a flat plate is

1. A ½ρAV² only always ✓
2. B ρgAH ✓
3. C ρAV² for normal impact when plate is stationary ✓
4. D zero for any angle ✓

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

1. A only weight of vane ✓
2. B change in momentum in flow direction ✓
3. C Manning n ✓
4. D Reynolds number alone ✓

Hydraulic jump occurs in open channel when

1. A subcritical becomes laminar pipe flow ✓
2. B flow becomes uniform always ✓
3. C supercritical flow transitions to subcritical flow ✓
4. D depth remains constant ✓

Specific force in open channel momentum analysis is

1. A Q/A only ✓
2. B Q²/(gA) + Aȳ ✓
3. C V²/(2g) ✓
4. D Manning V ✓

Impulse-momentum principle is preferred over Bernoulli when calculating

1. A static pressure at a point only ✓
2. B forces on bends, reducers and structures ✓
3. C capillary rise ✓
4. D vapour pressure ✓

Reynolds number Re is defined as

1. A ρVD/μ or VD/ν ✓
2. B μVD/ρ ✓
3. C ρgD/μ ✓
4. D V²D/g ✓

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

1. A 100 ✓
2. B 50000 ✓
3. C 10 ✓
4. D 2300 ✓

Laminar pipe flow velocity profile is

1. A uniform plug flow ✓
2. B linear from wall to centre ✓
3. C zero at centre ✓
4. D parabolic with maximum at centre ✓

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

1. A V ✓
2. B V² ✓
3. C V³ ✓
4. D independent of V ✓

Hydraulic radius R for full circular pipe equals

1. A D/2 ✓
2. B D/4 ✓
3. C πD²/4 ✓
4. D D ✓

Draft tube in reaction turbine serves to

1. A increase atmospheric pressure ✓
2. B measure discharge ✓
3. C filter sediment ✓
4. D recover kinetic energy and maintain suction head at runner ✓

Discharge over a rectangular sharp-crested weir is proportional to

1. A H only ✓
2. B H^(3/2) ✓
3. C H² ✓
4. D √H for all weir types ✓

V-notch weir is preferred for measuring

1. A very high floods only ✓
2. B groundwater seepage directly ✓
3. C low discharges with better sensitivity ✓
4. D pipe pressure only ✓

Coefficient of discharge for orifice is less than unity due to

1. A gravity variation ✓
2. B Manning n in pipe ✓
3. C contraction and energy losses ✓
4. D Coriolis effect ✓

Torricelli theorem gives jet velocity from orifice as

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

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

1. A n − k independent dimensionless groups ✓
2. B n + k groups ✓
3. C k − n groups ✓
4. D always one group ✓

Reynolds number is a dimensionless group representing ratio of

1. A gravity to viscosity ✓
2. B pressure to shear only ✓
3. C surface tension to gravity only ✓
4. D inertial forces to viscous forces ✓

Froude number similarity is essential in modeling

1. A free-surface gravity-driven flows ✓
2. B creeping laminar pipe flow only ✓
3. C Darcy groundwater flow ✓
4. D pure diffusion ✓

Geometric, kinematic and dynamic similarities together ensure

1. A only same colour of fluid ✓
2. B complete model-prototype similitude for intended laws ✓
3. C only same pipe material ✓
4. D only same temperature ✓