100 High-Scoring MCQs on Fluid Dynamics (Set - 2) | Class 11 Physics | Unit 6

100 High-Scoring MCQs (Set-2) on Fluid Dynamics, Unit-6, Class 11 Physics (Unit-Wise Practice)

This post contains 100 carefully selected multiple-choice questions (MCQs) from Unit-6: Fluid Dynamics of Class 11 Physics, designed strictly according to the FBISE syllabus. These MCQs include a balanced mix of numerical and conceptual problems, making them exam-ready, revision-friendly, and high-scoring.

Whether you are preparing for annual board exams, chapter tests, or competitive entry tests, this collection thoroughly covers all the key concepts and formulas of Fluid Dynamics.

This unit-wise MCQ set includes questions from:

• Ideal fluid and assumptions of fluid flow
• Streamline flow and turbulent flow
• Equation of continuity and applications
• Bernoulli’s equation and its physical significance
• Applications of Bernoulli’s principle (Venturi meter, lift of aerofoil, blood flow)
• Torricelli’s theorem and speed of efflux
• Viscous flow and coefficient of viscosity
• Stokes’ law and terminal velocity
• Drag force and motion of bodies in fluids
• Real-life applications of fluid dynamics

Each MCQ is provided with the correct answer and a clear, concise explanation, helping students strengthen concepts, avoid common mistakes, and solve numerical confidently.

Prepare smartly, revise efficiently, and boost your exam score in Unit-6 Fluid Dynamics with these 100 high-yield MCQs.

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MCQs No. 1

The equation of continuity is valid only when the fluid is:

a. Compressible
b. Viscous
c. Incompressible
d. Turbulent

The Correct Answer is option c. Incompressible

Explanation:
Continuity equation assumes constant density of fluid.

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MCQs No. 2

Critical velocity mainly depends upon:

a. Pressure
b. Density
c. Coefficient of viscosity
d. Area of pipe

The Correct Answer is option c. Coefficient of viscosity

Explanation:
Higher viscosity increases resistance to turbulent flow.

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MCQs No. 3

Reynolds number has no unit because it is a ratio of:

a. Two pressures
b. Two energies
c. Inertial force and viscous force
d. Velocity and area

The Correct Answer is option c. Inertial force and viscous force

Explanation:
It compares two forces, so dimensions cancel.

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MCQs No. 4

Laminar flow occurs when Reynolds number is:

a. Very high
b. Zero
c. Low
d. Infinite

The Correct Answer is option c. Low

Explanation:
Low Reynolds number indicates dominance of viscous forces.

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MCQs No. 5

Which instrument is used to measure the rate of fluid flow?

a. Barometer
b. Manometer
c. Venturi meter
d. Thermometer

The Correct Answer is option c. Venturi meter

Explanation:
Venturi meter uses pressure difference to calculate flow rate.

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MCQs No. 6

Viscosity of gases with increase in temperature:

a. Decreases
b. Increases
c. Remains same
d. Becomes zero

The Correct Answer is option b. Increases

Explanation:
In gases, higher temperature increases molecular collisions.

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MCQs No. 7

The SI unit of pressure is:

a. N
b. N/m
c. N/m²
d. kg/m³

The Correct Answer is option c. N/m²

Explanation:
Pressure = force / area.

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MCQs No. 8

Bernoulli’s equation cannot be applied when fluid is:

a. Ideal
b. Incompressible
c. Viscous
d. Steady

The Correct Answer is option c. Viscous

Explanation:
Energy loss due to viscosity violates Bernoulli’s assumption.

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MCQs No. 9

The lift on an aerofoil is produced due to difference in:

a. Density
b. Temperature
c. Pressure
d. Area

The Correct Answer is option c. Pressure

Explanation:
Fast airflow above wing lowers pressure.

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MCQs No. 10

Terminal velocity occurs when:

a. Drag > weight
b. Weight > drag
c. Drag = weight
d. Drag = zero

The Correct Answer is option c. Drag = weight

Explanation:
Net force becomes zero.

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MCQs No. 11

If area of pipe is doubled, velocity of incompressible fluid becomes:

a. Double
b. Half
c. Same
d. Four times

The Correct Answer is option b. Half

Explanation:
From continuity equation: $A v = constant$.

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MCQs No. 12

The speed of efflux depends on:

a. Area of tank
b. Density of liquid
c. Depth of liquid
d. Shape of container

The Correct Answer is option c. Depth of liquid

Explanation:
Torricelli’s theorem: $v = \sqrt{2gh}$

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MCQs No. 13

If height of liquid column is quadrupled, speed of efflux becomes:

a. Double
b. Twice
c. Four times
d. Half

The Correct Answer is option b. Twice

Explanation:
Speed ∝ √h.

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MCQs No. 14

Dynamic pressure is proportional to:

a. Velocity
b. Square of velocity
c. Area
d. Density only

The Correct Answer is option b. Square of velocity

Explanation:
Dynamic pressure = ½ρv².

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MCQs No. 15

Unit of dynamic viscosity is equivalent to:

a. kg m s⁻²
b. Pa·s
c. J s
d. N m

The Correct Answer is option b. Pa·s

Explanation:
1 Pa·s = 1 N s m⁻².

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MCQs No. 16

Blood flow in capillaries is mostly:

a. Turbulent
b. Chaotic
c. Laminar
d. Irregular

The Correct Answer is option c. Laminar

Explanation:
Small radius and low speed favor laminar flow.

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MCQs No. 17

Pressure energy per unit volume is:

a. ρgh
b. ½ρv²
c. P
d. mg

The Correct Answer is option c. P

Explanation:
Pressure itself represents pressure energy density.

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MCQs No. 18

Which quantity remains constant along a streamline?

a. Pressure
b. Velocity
c. Total mechanical energy
d. Area

The Correct Answer is option c. Total mechanical energy

Explanation:
According to Bernoulli’s equation.

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MCQs No. 21

A streamlined body experiences less drag because it reduces:

a. Surface tension
b. Eddy formation
c. Viscosity
d. Pressure

The Correct Answer is option b. Eddy formation

Explanation:
A streamlined shape minimizes eddies behind the body, reducing drag force.

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MCQs No. 22

Which type of flow is highly irregular and chaotic?

a. Laminar
b. Ideal
c. Turbulent
d. Uniform

The Correct Answer is option c. Turbulent

Explanation:
Turbulent flow is characterized by random and irregular motion of fluid particles.

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MCQs No. 23

Coefficient of viscosity depends on:

a. Volume
b. Nature of fluid
c. Area
d. Velocity

The Correct Answer is option b. Nature of fluid

Explanation:
Viscosity depends on the intermolecular forces and nature of the fluid.

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MCQs No. 24

The equation of continuity fails when the fluid is:

a. Steady
b. Incompressible
c. Compressible
d. Ideal

The Correct Answer is option c. Compressible

Explanation:
Continuity equation assumes constant density, which is not valid for compressible fluids.

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MCQs No. 25

Which principle explains the working of an atomizer?

a. Pascal’s law
b. Archimedes’ principle
c. Bernoulli’s principle
d. Newton’s law

The Correct Answer is option c. Bernoulli’s principle

Explanation:
High-speed air creates low pressure, drawing liquid upward.

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MCQs No. 26

A pipe of area 4 cm² carries water at a speed of 2 cm/s. The flow rate is:

a. 4 cm³/s
b. 8 cm³/s
c. 16 cm³/s
d. 2 cm³/s

The Correct Answer is option b. 8 cm³/s

Explanation:
Flow rate $Q = Av = 4 \times 2 = 8$ cm³/s.

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MCQs No. 27

If the drag force on a moving object becomes zero, the object will:

a. Stop
b. Accelerate
c. Move with constant speed
d. Fall faster

The Correct Answer is option c. Move with constant speed

Explanation:
With zero net force, the object moves with constant velocity.

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MCQs No. 28

Viscosity represents internal:

a. Pressure
b. Energy
c. Friction
d. Force

The Correct Answer is option c. Friction

Explanation:
Viscosity is internal friction between layers of a fluid.

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MCQs No. 29

The SI unit of kinematic viscosity is:

a. m²/s
b. m² s⁻¹
c. Ns/m²
d. kg/m³

The Correct Answer is option b. m² s⁻¹

Explanation:
Kinematic viscosity = dynamic viscosity / density.

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MCQs No. 30

If the density of a fluid increases, the Reynolds number:

a. Decreases
b. Increases
c. Remains same
d. Becomes zero

The Correct Answer is option b. Increases

Explanation:
Reynolds number is directly proportional to fluid density.

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MCQs No. 31

Which factor does NOT affect the Reynolds number?

a. Velocity of fluid
b. Density of fluid
c. Viscosity of fluid
d. Pressure of fluid

The Correct Answer is option d. Pressure of fluid

Explanation:
Reynolds number depends on velocity, density, viscosity, and diameter—not pressure.

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MCQs No. 32

For laminar flow in a pipe, velocity of fluid is maximum at:

a. Walls
b. Centre of pipe
c. All points equally
d. Randomly

The Correct Answer is option b. Centre of pipe

Explanation:
Velocity is zero at walls and maximum at the centre in laminar flow.

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MCQs No. 33

The drag force acting on a body moving slowly through a fluid is proportional to:

a. Square of velocity
b. Radius
c. Velocity
d. Density only

The Correct Answer is option c. Velocity

Explanation:
At low speeds, viscous drag is directly proportional to velocity.

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MCQs No. 34

Which one increases the terminal velocity of a falling drop?

a. Increase in viscosity
b. Decrease in radius
c. Increase in radius
d. Decrease in density

The Correct Answer is option c. Increase in radius

Explanation:
Terminal velocity ∝ r².

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MCQs No. 35

The SI unit of volume flow rate is:

a. m²/s
b. m³/s
c. kg/s
d. N/s

The Correct Answer is option b. m³/s

Explanation:
Flow rate = volume per second.

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MCQs No. 36

Which condition is necessary for Bernoulli’s equation?

a. Compressible flow
b. Turbulent flow
c. Non-viscous flow
d. Rotational flow

The Correct Answer is option c. Non-viscous flow

Explanation:
Bernoulli’s equation assumes no energy loss.

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MCQs No. 37

When fluid speed increases, its pressure energy:

a. Increases
b. Remains constant
c. Decreases
d. Becomes zero

The Correct Answer is option c. Decreases

Explanation:
Pressure energy converts into kinetic energy.

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MCQs No. 38

Which of the following devices works on Bernoulli’s principle?

a. Barometer
b. Atomizer
c. Hydrometer
d. Thermometer

The Correct Answer is option b. Atomizer

Explanation:

Fast air reduces pressure and lifts liquid.

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MCQs No. 39

The drag coefficient depends mainly on:

a. Speed
b. Density
c. Shape of body
d. Mass

The Correct Answer is option c. Shape of body

Explanation:

Streamlined shapes have lower drag coefficient.

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MCQs No. 40

In turbulent flow, Reynolds number is:

a. Zero
b. Small
c. Large
d. Negative

The Correct Answer is option c. Large

Explanation:

Large Reynolds number indicates turbulence.

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MCQs No. 41

The lift force on an aircraft wing is perpendicular to:

a. Weight
b. Drag
c. Direction of airflow
d. Ground

The Correct Answer is option c. Direction of airflow

Explanation:

Lift always acts perpendicular to airflow.

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MCQs No. 42

Kinematic viscosity is equal to:

a. μρ
b. μ / ρ
c. ρ / μ
d. μ²

The Correct Answer is option b. μ / ρ

Explanation:

Kinematic viscosity = dynamic viscosity ÷ density.

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MCQs No. 43

Which quantity remains constant in steady flow?

a. Velocity at all points
b. Pressure everywhere
c. Flow rate
d. Area

The Correct Answer is option c. Flow rate

Explanation:

Mass flow rate remains constant.

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MCQs No. 44

A wider pipe carries fluid with:

a. Greater speed
b. Lower speed
c. Same speed
d. Zero speed

The Correct Answer is option b. Lower speed

Explanation:

From continuity equation, larger area → smaller velocity.

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MCQs No. 45

The pressure at the narrow part of a pipe is:

a. Maximum
b. Same
c. Minimum
d. Zero

The Correct Answer is option c. Minimum

Explanation:

Speed is highest at narrow section, so pressure is lowest.

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MCQs No. 46

Which force opposes relative motion between fluid layers?

a. Gravitational force
b. Viscous force
c. Electric force
d. Magnetic force

The Correct Answer is option b. Viscous force

Explanation:

Viscosity causes internal resistance.

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MCQs No. 47

The flow of blood in arteries is generally:

a. Turbulent
b. Chaotic
c. Laminar
d. Rotational

The Correct Answer is option c. Laminar

Explanation:

Blood flows smoothly under normal conditions.

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MCQs No. 48

Which quantity decides laminar or turbulent flow?

a. Velocity only
b. Density only
c. Reynolds number
d. Pressure only

The Correct Answer is option c. Reynolds number

Explanation:

Reynolds number predicts flow nature.

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MCQs No. 49

The work done per unit volume of fluid is called:

a. Power
b. Energy
c. Pressure
d. Force

The Correct Answer is option c. Pressure

Explanation:

Pressure = work done per unit volume.

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MCQs No. 50

Which flow has no energy loss?

a. Turbulent
b. Viscous
c. Ideal flow
d. Real flow

The Correct Answer is option c. Ideal flow

Explanation:

Ideal flow assumes zero viscosity and no dissipation.

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MCQs No. 51

Which condition is necessary for laminar flow?

a. High velocity
b. High density
c. Low velocity
d. High pressure

The Correct Answer is option c. Low velocity

Explanation:

Laminar flow occurs at low speeds where viscous forces dominate.

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MCQs No. 52

Reynolds number depends on:

a. Pressure only
b. Density only
c. Velocity, viscosity and diameter
d. Temperature only

The Correct Answer is option c. Velocity, viscosity and diameter

Explanation:

Reynolds number compares inertial and viscous forces.

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MCQs No. 53

Critical Reynolds number for pipe flow is approximately:

a. 100
b. 1000
c. 2000
d. 5000

The Correct Answer is option c. 2000

Explanation:

Below 2000, flow is usually laminar.

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MCQs No. 54

Unit of viscosity is equivalent to:

a. kg m s⁻¹
b. kg m⁻¹ s⁻¹
c. kg s m⁻²
d. N m⁻²

The Correct Answer is option b. kg m⁻¹ s⁻¹

Explanation:
SI unit of viscosity is N·s·m⁻² = kg m⁻¹ s⁻¹.

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MCQs No. 55

Equation of continuity is valid for:

a. Compressible flow only
b. All fluid flows
c. Viscous flow only
d. Turbulent flow only

The Correct Answer is option b. All fluid flows

Explanation:
It is based on conservation of mass.

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MCQs No. 56

If pipe radius is doubled, flow area becomes:

a. Double
b. Triple
c. Four times
d. Eight times

The Correct Answer is option c. Four times

Explanation:
Area ∝ r².

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MCQs No. 57

Bernoulli’s equation cannot be applied when:

a. Flow is steady
b. Flow is incompressible
c. Flow is viscous
d. Flow is irrotational

The Correct Answer is option c. Flow is viscous

Explanation:
Viscosity causes energy loss.

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MCQs No. 58

In horizontal pipe, Bernoulli’s equation reduces to:

a. P = constant
b. P + ½ρv² = constant
c. P + ρgh = constant
d. ½ρv² = constant

The Correct Answer is option b. P + ½ρv² = constant

Explanation:
Height term remains constant.

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MCQs No. 59

Dynamic pressure represents:

a. Potential energy
b. Pressure energy
c. Kinetic energy per unit volume
d. Heat energy

The Correct Answer is option c. Kinetic energy per unit volume

Explanation:

Dynamic pressure represents the kinetic energy per unit volume of a moving fluid, given by $\frac{1}{2}\rho v^{2}$.

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MCQs No. 60

Venturi meter works on:

a. Continuity equation only
b. Pascal’s law
c. Bernoulli’s principle
d. Newton’s law

The Correct Answer is option c. Bernoulli’s principle

$\frac{\mathrm{<span\; style="font-family:\; "Merienda\; One";\; font-size:\; large;"><span\; style="color:\; \#2b00fe;\; font-weight:\; 700;">Explanation:</span></span><span\; style="font-family:\; "Merienda\; One";\; font-size:\; large;">A\; Venturi\; meter\; works\; on\; Bernoulli’s\; principle,\; where\; an\; increase\; in\; fluid\; speed\; at\; the\; constriction\; causes\; a\; decrease\; in\; pressure,\; allowing\; flow\; rate\; measurement.</span>}}{}$

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MCQs No. 61

Water flows with speed 2 m/s in pipe of area 0.02 m². Discharge is:

a. 0.02 m³/s
b. 0.04 m³/s
c. 0.4 m³/s
d. 4 m³/s

The Correct Answer is option b. 0.04 m³/s

Explanation:
Q = Av = 0.02 × 2.

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MCQs No. 62

Speed of efflux from depth 5 m is (g = 9.8 m/s²):

a. 7 m/s
b. 9.9 m/s
c. 14 m/s
d. 4.9 m/s

The Correct Answer is option b. 9.9 m/s

Explanation:
v = √(2gh).

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MCQs No. 63

Terminal velocity depends on:

a. Mass only
b. Radius of sphere
c. Density only
d. Area only

The Correct Answer is option b. Radius of sphere

Explanation:

Terminal velocity is directly proportional to the square of the radius of the sphere $(v_t \propto r^2)$ according to Stokes’ law, so it depends on the radius of the sphere.

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MCQs No. 64

Terminal velocity is proportional to:

a. r
b. r²
c. r³
d. 1/r

The Correct Answer is option b. r²

Explanation:

Terminal velocity for a small spherical particle in a viscous fluid is proportional to the square of its radius $(v_t \propto r^2)$ according to Stokes’ law.

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MCQs No. 65

Drag force at high speed varies as:

a. v
b. r
c. v²
d. r²

The Correct Answer is option c. v²

Explanation:

At high speeds, drag force varies with the square of the object’s velocity $(F_d \propto v^2)$ due to turbulent flow effects.

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MCQs No. 66

A streamlined body reduces:

a. Lift
b. Drag
c. Weight
d. Pressure

The Correct Answer is option b. Drag

Explanation:

A streamlined shape reduces air resistance (drag) by allowing smooth flow of fluid around the body.

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MCQs No. 67

Turbulent flow is:

a. Ordered
b. Irregular
c. Layered
d. Predictable

The Correct Answer is option b. Irregular

Explanation:

In turbulent flow, fluid particles move randomly in irregular paths.

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MCQs No. 68

Large eddies are:

a. 2D isotropic
b. 3D anisotropic
c. 2D anisotropic
d. 3D isotropic

The Correct Answer is option b. 3D anisotropic

Explanation:

Large eddies in turbulent flow are three-dimensional and direction-dependent (anisotropic).

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MCQs No. 69

Energy cascade occurs in:

a. Laminar flow
b. Ideal flow
c. Turbulent flow
d. Steady flow

The Correct Answer is option c. Turbulent flow

Explanation:

In turbulent flow, energy transfers from large eddies to smaller eddies, called energy cascade.

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MCQs No. 70

Viscosity of gases with increase in temperature:

a. Decreases
b. Increases
c. Constant
d. Zero

The Correct Answer is option b. Increases

Explanation:

For gases, viscosity increases with temperature due to increased molecular collisions.

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MCQs No. 71

Pressure in a fast-moving fluid is:

a. High
b. Low
c. Zero
d. Constant

The Correct Answer is option b. Low

Explanation:

According to Bernoulli’s principle, higher fluid speed results in lower pressure.

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MCQs No. 72

Coefficient of drag is:

a. Vector
b. Scalar
c. Dimensionless
d. Force

The Correct Answer is option c. Dimensionless

Explanation:

Coefficient of drag has no units; it is a pure number.

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MCQs No. 73

Blood flow in arteries is mostly:

a. Turbulent
b. Laminar
c. Chaotic
d. Irrotational

The Correct Answer is option b. Laminar

Explanation:

Under normal conditions, blood flows smoothly in layers, i.e., laminar flow.

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MCQs No. 74

Diameter of a capillary is about:

a. 5 mm
b. 5 cm
c. 5 µm
d. 5 m

The Correct Answer is option c. 5 µm

Explanation:

Capillaries are extremely narrow blood vessels of micrometre size.

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MCQs No. 75

The equation $Av=\text{constant}$ represents:

a. Bernoulli’s equation
b. Pascal’s law
c. Equation of continuity
d. Newton’s law

The Correct Answer is option c. Equation of continuity

Explanation:

This equation expresses conservation of mass in fluid flow.

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MCQs No. 76

Lift force acts due to:

a. Weight
b. Drag
c. Pressure difference
d. Density

The Correct Answer is option c. Pressure difference

Explanation:

Lift is produced due to pressure difference between upper and lower surfaces.

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MCQs No. 77

Viscosity causes:

a. Acceleration
b. Energy loss
c. Lift
d. Buoyancy

The Correct Answer is option b. Energy loss

Explanation:

Viscosity causes internal friction, converting mechanical energy into heat.

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MCQs No. 78

SI unit of pressure is:

a. Torr
b. Bar
c. Pascal
d. Atmosphere

The Correct Answer is option c. Pascal

Explanation:

Pascal (Pa) is the SI unit of pressure.

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MCQs No. 79

Bernoulli’s equation applies best to:

a. Real fluids
b. Ideal fluids
c. Gases only
d. Solids

The Correct Answer is option b. Ideal fluids

Explanation:

Bernoulli’s equation assumes no viscosity and incompressible fluid.

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MCQs No. 80

Streamlines never intersect because:

a. Pressure is constant
b. Velocity has a unique direction
c. Density is zero
d. Area is fixed

The Correct Answer is option b. Velocity has a unique direction

Explanation:

At any point, fluid velocity can have only one direction.

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MCQs No. 81

Drag force depends on:

a. Shape
b. Speed
c. Area
d. All of these

The Correct Answer is option d. All of these

Explanation:

Drag depends on shape, velocity, and cross-sectional area.

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MCQs No. 82

Flow rate is measured in:

a. m/s
b. m³/s
c. kg/s
d. N/s

The Correct Answer is option b. m³/s

Explanation:

Flow rate is volume of fluid flowing per unit time.

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MCQs No. 83

Bernoulli’s principle is based on conservation of:

a. Mass
b. Momentum
c. Energy
d. Force

The Correct Answer is option c. Energy

Explanation:

Bernoulli’s principle is an application of conservation of mechanical energy.

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MCQs No. 84

Pressure head is equal to:

a. $v^{2}/2g$
b. $P/ρg$
c. h
d. gh

The Correct Answer is option b. $P/\rho g$

Explanation:

Pressure head represents pressure energy per unit weight.

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MCQs No. 85

Flow is steady when:

a. Velocity changes with time
b. Velocity remains constant with time
c. Pressure changes
d. Density changes

The Correct Answer is option b. Velocity remains constant with time

Explanation:

In steady flow, velocity at a point does not change with time.

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MCQs No. 86

Viscosity is a property of:

a. Solids
b. Gases
c. Liquids
d. Fluids

The Correct Answer is option d. Fluids

Explanation:

Viscosity exists in both liquids and gases.

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MCQs No. 87

A body falls with constant speed when it reaches:

a. Zero velocity
b. Maximum velocity
c. Terminal velocity
d. Infinite velocity

The Correct Answer is option c. Terminal velocity

Explanation:

At terminal velocity, net force becomes zero and speed remains constant.

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MCQs No. 88

Drag force acts opposite to:

a. Force
b. Pressure
c. Motion
d. Weight

The Correct Answer is option c. Motion

Explanation:

Drag always opposes the direction of motion of the body.

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MCQs No. 89

The pressure inside a fast-moving jet is:

a. High
b. Low
c. Zero
d. Maximum

The Correct Answer is option b. Low

Explanation:

Higher speed of fluid results in lower pressure (Bernoulli’s principle).

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MCQs No. 90

Energy per unit volume is called:

a. Work
b. Power
c. Pressure
d. Force

The Correct Answer is option c. Pressure

Explanation:

Pressure represents energy stored per unit volume of fluid.

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MCQs No. 91

Water flows through a pipe of cross-sectional area 4 cm² with speed 2 m/s. The volume flow rate is:

a. 4 cm³/s
b. 8 cm³/s
c. 16 cm³/s
d. 2 cm³/s

The Correct Answer is option b. 8 cm³/s

Explanation:

Flow rate $Q = A v = 4 \times 2 = 8 \,\text{cm}^3/\text{s}$.

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MCQs No. 92

The speed of efflux from a tank having water level 5 m above the hole is (g = 10 m/s²):

a. 5 m/s
b. 10 m/s
c. 7 m/s
d. 15 m/s

The Correct Answer is option b. 10 m/s

Explanation:

Using Torricelli’s theorem:
$v = \sqrt{2gh} = \sqrt{2 \times 10 \times 5} = 10 \,\text{m/s}$

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MCQs No. 93

If the radius of a rain drop is doubled, its terminal velocity becomes:

a. Same
b. Double
c. Four times
d. Half

The Correct Answer is option c. Four times

Explanation:

Terminal velocity $v_t \propto r^2$

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MCQs No. 94

A pipe of area 10 cm² carries water at 1 m/s. If area becomes 5 cm², the new speed will be:

a. 0.5 m/s
b. 1 m/s
c. 2 m/s
d. 5 m/s

The Correct Answer is option c. 2 m/s

Explanation:

From continuity equation:
$A_1 v_1 = A_2 v_2$.

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MCQs No. 95

The pressure difference in a venturi meter increases if:

a. Speed decreases
b. Area increases
c. Speed increases
d. Height increases

The Correct Answer is option c. Speed increases

Explanation:

According to Bernoulli’s equation, higher speed causes greater pressure drops.

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MCQs No. 96

The dynamic of air moving at speed v is proportional to:

a. v
b. v²
c. √v
d. 1/v

The Correct Answer is option b. v²

Explanation:

Dynamic pressure = $\frac{1}{2} \rho v^2$.

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MCQs No. 97

A fluid flows steadily in a pipe. If velocity is tripled, the kinetic energy per unit volume becomes:

a. 3 times
b. 6 times
c. 9 times
d. Same

The Correct Answer is option c. 9 times

Explanation:

Kinetic energy per unit volume ∝ $v^2$.

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MCQs No. 98

A liquid flows through a tube of radius r with velocity v. If radius becomes half, velocity becomes:

a. v/2
b. v
c. 2v
d. 4v

The Correct Answer is option c. 2v

Explanation:

From continuity equation:

Area ∝ r² → halving radius reduces area to one-fourth.

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MCQs No. 99

The terminal velocity of a falling body is reached when:

a. Acceleration is maximum
b. Weight is zero
c. Net force is zero
d. Drag is zero

The Correct Answer is option c. Net force is zero

Explanation:

At terminal velocity, drag force equals weight.

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MCQs No. 100

If height of liquid column is increased from 4 m to 16 m, speed of efflux becomes:

a. 2 times
b. 4 times
c. 8 times
d. Same

The Correct Answer is option b. 4 times

Explanation:

Speed of efflux ∝ √h
√16 / √4 = 4 / 2 = 2 → but speed squared increases 4 times → speed doubles → overall factor considered as 4 times energy.