39 real Fluid Mechanics questions from the Mechanical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Pascal's law?
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A.sum of pressure head, velocity head and elevation head stays constant along a streamline for steady, incompressible, inviscid flow
B.pressure applied to a confined fluid at rest is transmitted undiminished in every direction, the principle behind hydraulic jacks and presses
C.distance between the centre of gravity and the metacentre of a floating body, which must be positive for stable equilibrium
D.detachment of flow from a surface under an adverse pressure gradient, creating a wake and a large pressure drag
2. Which term means: "pressure applied to a confined fluid at rest is transmitted undiminished in every direction, the principle behind hydraulic jacks and presses"?
A.Pascal's law — detachment of flow from a surface under an adverse pressure gradient, creating a wake and a large pressure drag
B.Pascal's law — head loss in a pipe hf = fLV²/2gD, with the friction factor read from the Moody chart for turbulent flow
C.Pascal's law — ratio of inertia to viscous forces ρVD/μ, with pipe flow laminar below about 2000 and fully turbulent above 4000
D.Pascal's law — pressure applied to a confined fluid at rest is transmitted undiminished in every direction, the principle behind hydraulic jacks and presses
5. Which term means: "sum of pressure head, velocity head and elevation head stays constant along a streamline for steady, incompressible, inviscid flow"?
A.Bernoulli's equation — vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required
B.Bernoulli's equation — the statement that mass flow rate is conserved along a streamtube, so density times area times velocity stays constant in steady flow
C.Bernoulli's equation — pressure applied to a confined fluid at rest is transmitted undiminished in every direction, the principle behind hydraulic jacks and presses
D.Bernoulli's equation — sum of pressure head, velocity head and elevation head stays constant along a streamline for steady, incompressible, inviscid flow
A.Reynolds number — vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required
B.Reynolds number — sum of pressure head, velocity head and elevation head stays constant along a streamline for steady, incompressible, inviscid flow
C.Reynolds number — the distance by which a boundary would have to be shifted outward for an ideal fluid to carry the same mass flow deficit as the real boundary layer
D.Reynolds number — ratio of inertia to viscous forces ρVD/μ, with pipe flow laminar below about 2000 and fully turbulent above 4000
A.Metacentric height — head loss in a pipe hf = fLV²/2gD, with the friction factor read from the Moody chart for turbulent flow
B.Metacentric height — the distance by which a boundary would have to be shifted outward for an ideal fluid to carry the same mass flow deficit as the real boundary layer
C.Metacentric height — distance between the centre of gravity and the metacentre of a floating body, which must be positive for stable equilibrium
D.Metacentric height — the ratio of inertia to gravity forces, which classifies open-channel flow as subcritical, critical or supercritical
A.Darcy-Weisbach equation — distance between the centre of gravity and the metacentre of a floating body, which must be positive for stable equilibrium
B.Darcy-Weisbach equation — ratio of inertia to viscous forces ρVD/μ, with pipe flow laminar below about 2000 and fully turbulent above 4000
C.Darcy-Weisbach equation — the ratio of inertia to gravity forces, which classifies open-channel flow as subcritical, critical or supercritical
D.Darcy-Weisbach equation — head loss in a pipe hf = fLV²/2gD, with the friction factor read from the Moody chart for turbulent flow
A.Hagen-Poiseuille flow — detachment of flow from a surface under an adverse pressure gradient, creating a wake and a large pressure drag
B.Hagen-Poiseuille flow — the distance by which a boundary would have to be shifted outward for an ideal fluid to carry the same mass flow deficit as the real boundary layer
C.Hagen-Poiseuille flow — laminar pipe flow in which friction factor is 64/Re and pressure drop is proportional to viscosity, length and flow rate
D.Hagen-Poiseuille flow — sum of pressure head, velocity head and elevation head stays constant along a streamline for steady, incompressible, inviscid flow
A.Boundary layer separation — sum of pressure head, velocity head and elevation head stays constant along a streamline for steady, incompressible, inviscid flow
B.Boundary layer separation — vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required
C.Boundary layer separation — index N√Q/H^0.75 that classifies impeller shape from radial (low values) to axial (high values) for a given duty
D.Boundary layer separation — detachment of flow from a surface under an adverse pressure gradient, creating a wake and a large pressure drag
A.ratio of inertia to viscous forces ρVD/μ, with pipe flow laminar below about 2000 and fully turbulent above 4000
B.distance between the centre of gravity and the metacentre of a floating body, which must be positive for stable equilibrium
C.pressure applied to a confined fluid at rest is transmitted undiminished in every direction, the principle behind hydraulic jacks and presses
D.vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required
23. Which term means: "vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required"?
A.Cavitation in pumps — distance between the centre of gravity and the metacentre of a floating body, which must be positive for stable equilibrium
B.Cavitation in pumps — a scalar whose constant-value lines are streamlines and whose difference between two streamlines equals the volume flow rate between them
C.Cavitation in pumps — vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required
D.Cavitation in pumps — head loss in a pipe hf = fLV²/2gD, with the friction factor read from the Moody chart for turbulent flow
A.vapour bubbles form where local pressure falls below vapour pressure and collapse on the impeller, avoided by keeping NPSH available above NPSH required
B.index N√Q/H^0.75 that classifies impeller shape from radial (low values) to axial (high values) for a given duty
C.a scalar whose constant-value lines are streamlines and whose difference between two streamlines equals the volume flow rate between them
D.laminar pipe flow in which friction factor is 64/Re and pressure drop is proportional to viscosity, length and flow rate
A.Specific speed of a pump — pressure applied to a confined fluid at rest is transmitted undiminished in every direction, the principle behind hydraulic jacks and presses
B.Specific speed of a pump — laminar pipe flow in which friction factor is 64/Re and pressure drop is proportional to viscosity, length and flow rate
C.Specific speed of a pump — a scalar whose constant-value lines are streamlines and whose difference between two streamlines equals the volume flow rate between them
D.Specific speed of a pump — index N√Q/H^0.75 that classifies impeller shape from radial (low values) to axial (high values) for a given duty
29. Which term means: "the statement that mass flow rate is conserved along a streamtube, so density times area times velocity stays constant in steady flow"?
A.Continuity equation — distance between the centre of gravity and the metacentre of a floating body, which must be positive for stable equilibrium
B.Continuity equation — the ratio of inertia to gravity forces, which classifies open-channel flow as subcritical, critical or supercritical
C.Continuity equation — the statement that mass flow rate is conserved along a streamtube, so density times area times velocity stays constant in steady flow
D.Continuity equation — index N√Q/H^0.75 that classifies impeller shape from radial (low values) to axial (high values) for a given duty
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