Q.1 Which of the following quantities is a scalar in fluid mechanics?
Velocity
Pressure
Acceleration
Force
Explanation - Pressure in a fluid has magnitude only and no direction, making it a scalar quantity.
Correct answer is: Pressure
Q.2 The SI unit of viscosity is:
N·s/m²
Pa
kg/m³
m²/s
Explanation - Dynamic viscosity is measured in Pascal-second, which is equivalent to N·s/m².
Correct answer is: N·s/m²
Q.3 Continuity equation is based on the principle of:
Conservation of mass
Conservation of momentum
Conservation of energy
Conservation of pressure
Explanation - The continuity equation states that mass entering and leaving a fluid system must remain conserved.
Correct answer is: Conservation of mass
Q.4 Which of the following assumptions is made in Bernoulli’s theorem?
Flow is turbulent
Fluid is compressible
Flow is steady and non-viscous
Flow has heat transfer
Explanation - Bernoulli’s theorem applies to steady, incompressible, non-viscous, and irrotational flow.
Correct answer is: Flow is steady and non-viscous
Q.5 The pressure at a depth h in a liquid of density ρ is given by:
ρgh
ρ/h
ρg/h
ρh/g
Explanation - Pressure increases linearly with depth according to P = ρgh.
Correct answer is: ρgh
Q.6 Reynolds number is a ratio of:
Inertial force to viscous force
Viscous force to inertial force
Pressure force to gravitational force
Elastic force to viscous force
Explanation - Reynolds number = (Inertial force)/(Viscous force) and determines laminar or turbulent flow.
Correct answer is: Inertial force to viscous force
Q.7 Streamline flow occurs when Reynolds number is:
< 2000
> 4000
2000–4000
Independent of Reynolds number
Explanation - For Re < 2000, flow remains laminar and smooth.
Correct answer is: < 2000
Q.8 Which instrument measures fluid pressure?
Thermometer
Barometer
Hygrometer
Ammeter
Explanation - A barometer is used to measure pressure in fluids (commonly atmospheric pressure).
Correct answer is: Barometer
Q.9 A body floats in water when:
Weight < Buoyant force
Weight > Buoyant force
Weight = Buoyant force
None of these
Explanation - Floating occurs when the upward buoyant force equals the downward gravitational force.
Correct answer is: Weight = Buoyant force
Q.10 Viscosity decreases with:
Increase in temperature for gases
Increase in temperature for liquids
Decrease in temperature for gases
No change with temperature
Explanation - Viscosity of liquids decreases as temperature rises due to weaker intermolecular forces.
Correct answer is: Increase in temperature for liquids
Q.11 Surface tension is due to:
Adhesive forces
Cohesive forces
Gravitational forces
Buoyant forces
Explanation - Surface tension originates from cohesive molecular forces at the liquid surface.
Correct answer is: Cohesive forces
Q.12 Which equation relates discharge with velocity and area?
Bernoulli’s equation
Poiseuille’s equation
Continuity equation
Navier-Stokes equation
Explanation - The continuity equation states Q = A × v, where Q is discharge.
Correct answer is: Continuity equation
Q.13 Which type of flow is characterized by random fluctuations?
Laminar flow
Turbulent flow
Steady flow
Uniform flow
Explanation - Turbulent flow involves chaotic, random velocity fluctuations.
Correct answer is: Turbulent flow
Q.14 Which of the following is dimensionless?
Viscosity
Velocity
Reynolds number
Pressure
Explanation - Reynolds number is a dimensionless quantity used in fluid mechanics.
Correct answer is: Reynolds number
Q.15 Which of the following fluids is considered incompressible?
Air
Steam
Water
Oxygen
Explanation - Liquids like water are nearly incompressible under normal conditions.
Correct answer is: Water
Q.16 The upward force acting on a body immersed in a fluid is called:
Lift
Drag
Buoyant force
Viscous force
Explanation - According to Archimedes’ principle, a buoyant force acts upward on immersed bodies.
Correct answer is: Buoyant force
Q.17 Navier-Stokes equations are based on:
Conservation of momentum
Conservation of energy
Conservation of charge
Conservation of angular momentum
Explanation - Navier-Stokes equations describe fluid motion using conservation of momentum.
Correct answer is: Conservation of momentum
Q.18 Capillary rise is greater when:
Tube radius is larger
Tube radius is smaller
Liquid is more dense
Surface tension is low
Explanation - Capillary rise is inversely proportional to the radius of the tube.
Correct answer is: Tube radius is smaller
Q.19 Poiseuille’s law deals with:
Viscous flow in a pipe
Turbulent flow in a river
Compressible flow in gases
Hydrostatic pressure
Explanation - Poiseuille’s law gives the flow rate of a viscous fluid through a cylindrical tube.
Correct answer is: Viscous flow in a pipe
Q.20 When an object moves in a fluid, the opposing force is called:
Lift
Drag
Buoyant force
Surface tension
Explanation - Drag is the resistive force exerted by the fluid on a moving object.
Correct answer is: Drag
Q.21 Which principle explains the working of a carburetor?
Archimedes’ principle
Bernoulli’s principle
Pascal’s law
Reynolds’ law
Explanation - Carburetors use Bernoulli’s principle to mix air and fuel efficiently.
Correct answer is: Bernoulli’s principle
Q.22 The pressure at a point in a fluid at rest is:
Equal in all directions
Greater downward
Greater upward
Zero
Explanation - Pascal’s law states that fluid pressure at rest is isotropic (equal in all directions).
Correct answer is: Equal in all directions
Q.23 Which of the following is not a property of ideal fluids?
Incompressibility
No viscosity
Irrotational flow
High density
Explanation - Ideal fluids are assumed incompressible and non-viscous, but density may not necessarily be high.
Correct answer is: High density
Q.24 The velocity profile for laminar flow in a pipe is:
Parabolic
Linear
Exponential
Uniform
Explanation - In laminar flow through a circular pipe, velocity distribution is parabolic.
Correct answer is: Parabolic
Q.25 The condition for dynamic similarity between two flows is:
Same velocity
Same Reynolds number
Same pressure
Same viscosity
Explanation - Dynamic similarity requires equality of Reynolds numbers between two systems.
Correct answer is: Same Reynolds number