PlacementPrepPressure at a depth h in a liquid of density ρ is:
Solution
Hydrostatic pressure increases linearly with depth.
Answer: (A) ρgh
Technical · Mechanical Engineering
Fluid Mechanics and Machines MCQs for placement tests
20 technical questions of moderate difficulty, as asked in campus placement and company tests. Each has a short explanation.
Pascal's law states that pressure in a fluid at rest is:
Solution
This principle is used in hydraulic jacks.
Answer: (C) Equal in all directions
Bernoulli's equation is based on the conservation of:
Solution
Pressure, kinetic and potential energy per unit weight remain constant along a streamline.
Answer: (B) Energy
The continuity equation is based on the conservation of:
Solution
A₁V₁ = A₂V₂ for incompressible flow.
Answer: (D) Mass
Water flows through a pipe of area 0.02 m² at 3 m/s. In a section of area 0.01 m², the velocity is:
Solution
A₁V₁ = A₂V₂ gives V₂ = 0.02 × 3 / 0.01 = 6 m/s.
Answer: (A) 6 m/s
Flow is laminar in a pipe when the Reynolds number is less than about:
Solution
Above about 4000 it is turbulent; between is transitional.
Answer: (C) 2000
The Reynolds number is the ratio of:
Solution
Re = ρVD/μ.
Answer: (C) Inertia force to viscous force
A venturimeter is used to measure:
Solution
It uses the pressure drop at a throat to find discharge.
Answer: (D) Flow rate
A Pitot tube is used to measure:
Solution
It converts velocity head into a pressure reading.
Answer: (B) Flow velocity
The viscosity of a liquid with increasing temperature:
Solution
For gases it increases with temperature.
Answer: (D) Decreases
Cavitation in pumps is caused by:
Solution
Vapour bubbles form and collapse, damaging surfaces.
Answer: (A) Local pressure falling below the vapour pressure
A Pelton wheel is a:
Solution
Water jets strike buckets at atmospheric pressure.
Answer: (A) Impulse turbine for high heads
A Kaplan turbine is suited for:
Solution
It is an axial-flow reaction turbine.
Answer: (B) Low head and high discharge
The Darcy-Weisbach equation is used to calculate:
Solution
hf = fLV²/(2gD).
Answer: (A) Head loss due to friction in pipes
Surface tension is measured in:
Solution
It is force per unit length.
Answer: (D) N/m
The unit of dynamic viscosity in SI is:
Solution
Kinematic viscosity is measured in m²/s.
Answer: (C) Pa·s
Buoyant force on a submerged body equals:
Solution
This is Archimedes' principle.
Answer: (A) The weight of the fluid displaced
A floating body is stable when its metacentre is:
Solution
A positive metacentric height gives stability.
Answer: (C) Above the centre of gravity
The velocity of flow from an orifice under a head h is ideally:
Solution
Torricelli's theorem.
Answer: (A) √(2gh)
A centrifugal pump must be primed because:
Solution
Air has too low a density to create the needed pressure difference.
Answer: (C) It cannot create enough suction with air in the casing
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