Fluid Dynamics MCQs
Which of the following solids is characterized by a regular, repeating arrangement of atoms or molecules throughout its structure?
Amorphous Solid
Crystalline Solid
Polymeric Solid
Glassy Solid
A force of 500 N is applied to a wire with a cross-sectional area of 2 × 10⁻⁶ m². What is the tensile stress on the wire?
2.5 × 10⁸ Pa
1 × 10⁻³ Pa
4 × 10⁻⁹ Pa
250 Pa
What does the area under a force-extension graph represent for a material deformed within its elastic limit?
Young's Modulus
Elastic Potential Energy
Tensile Strength
Spring Constant
According to Archimedes' principle, the upward buoyant force on a submerged object is equal to the:
Weight of the object in air
Volume of the fluid displaced by the object
Weight of the fluid displaced by the object
Mass of the object
A submarine increases its weight by filling its ballast tanks with seawater. It will begin to sink when:
Its weight is less than the upthrust
Its weight is equal to the upthrust
Its weight becomes greater than the upthrust
It displaces a volume of water equal to its own volume
Which type of fluid flow is characterized by smooth, parallel layers where particles follow the same path as preceding particles?
Turbulent Flow
Compressible Flow
Viscous Flow
Streamline Flow
The equation of continuity (A₁v₁ = A₂v₂) is a direct consequence of which fundamental principle?
Conservation of Energy
Conservation of Momentum
Conservation of Mass
Newton's Third Law
A gardener puts a thumb over the end of a hose to make the water spray farther. This action demonstrates:
Bernoulli's Principle
The Equation of Continuity
Archimedes' Principle
Pascal's Law
According to Bernoulli's principle, if the speed of a fluid increases, what happens to its internal pressure?
It increases
It remains constant
It decreases
It depends on the fluid's viscosity
The lift on an airplane wing is primarily generated by a pressure difference. Where is the pressure lower?
On the bottom surface of the wing
On the top surface of the wing
At the leading edge of the wing
The pressure is the same on both surfaces
The retarding force experienced by an object moving through a fluid is known as:
Upthrust
Weight
Drag Force
Terminal Force
An object falling through a fluid reaches terminal velocity when:
The force of gravity on it is zero
The drag force becomes equal to its weight
It stops accelerating
The upthrust equals its weight
Which of these materials is an example of an amorphous or glassy solid?
Diamond
Sodium Chloride
Glass
Copper
Strain is defined as the fractional change in a property. What are the SI units of tensile strain?
Pascals (Pa)
Newtons (N)
Meters (m)
It is dimensionless
A steel wire and a rubber band of the same length and cross-sectional area are subjected to the same stretching force. Which one will have a higher Young's Modulus?
The rubber band
The steel wire
They will have the same Young's Modulus
It cannot be determined without knowing the extension
What is the point on a stress-strain curve beyond which a material will not return to its original shape after the stress is removed?
Proportional Limit
Elastic Limit
Fracture Point
Ultimate Tensile Strength
A large ship made of steel floats, while a small steel bolt sinks. This is because the ship:
Is less dense than the bolt
Has a shape that displaces a large volume of water
Has a smaller mass-to-volume ratio than the bolt
Is hollow, making it lighter than water
A fluid is considered 'ideal' for simplifying calculations. Which of the following is NOT a property of an ideal fluid?
The flow is steady
The fluid is incompressible
The fluid is viscous
The flow is irrotational
A river flows from a wide section into a narrow gorge. According to the equation of continuity, the speed of the water in the narrow gorge will:
Increase
Decrease
Remain the same
Become turbulent
A Venturi meter is used to measure the speed of a fluid in a pipe. It works by measuring the:
Temperature change in a constricted section
Pressure difference between a wide and a narrow section
Change in the fluid's viscosity
Height difference of the entire pipe
Torricelli's theorem (v = √(2gh)) calculates the speed of efflux from an orifice in a tank. This speed is equivalent to the speed an object would have after:
Being thrown upwards with an initial velocity v
Falling freely from a height h
Sliding down a frictionless ramp of height h
Being submerged to a depth h
According to Stokes' Law, the drag force on a small sphere is directly proportional to all of the following EXCEPT:
The viscosity of the fluid (η)
The radius of the sphere (r)
The velocity of the sphere (v)
The density of the fluid (ρ)
A paratrooper jumps from a plane. They reach a terminal velocity, then open their parachute and reach a new, lower terminal velocity. Why is the second terminal velocity lower?
The paratrooper's mass decreases
The force of gravity is weaker closer to the ground
The parachute increases the surface area and drag force
The density of the air increases significantly
In the context of blood flow, arteriosclerosis (narrowing of the arteries) can be dangerous. According to Bernoulli's principle, the pressure inside a narrowed section of an artery is:
Higher than in the surrounding, wider sections
Lower than in the surrounding, wider sections
The same as in the wider sections, but the blood moves faster
Dependent only on the heart's pumping force
Which property of a fluid is a measure of its internal friction or resistance to flow?
Density
Viscosity
Compressibility
Surface Tension
The transition from laminar to turbulent flow occurs when:
The fluid's viscosity remains constant
The fluid's velocity decreases
The fluid's velocity exceeds critical speed
The fluid becomes incompressible
A spring with a spring constant of k = 400 N/m is stretched by 0.2 m. How much elastic potential energy is stored in the spring?
What is a key characteristic of a superfluid?
Infinite density
Extremely high temperature
Zero viscosity
Solid crystalline structure
A perfume bottle atomizer works by blowing a fast stream of air across the top of a tube dipped in the perfume. This causes the perfume to rise and spray out because the fast-moving air has:
High pressure, which pushes the liquid up
Low pressure, which pushes the liquid up
High viscosity, which pulls the liquid up
Low density, which creates a vacuum
If the terminal velocity of a spherical raindrop of radius 'r' is 'v', what would be the approximate terminal velocity of a spherical raindrop of radius '2r' (assuming all other factors are constant)?
The property of a body to return to its original shape and size after the removal of a deforming force is called:
Plasticity
Elasticity
Ductility
Brittleness
Hooke's Law states that stress is directly proportional to strain. In which region of the stress-strain curve is this law obeyed?
The entire elastic region
The plastic region
The proportional limit region
The fracture point
A wooden cube with a volume of 0.01 m³ is fully submerged in water (density ≈ 1000 kg/m³). What is the buoyant force acting on it? (Use g ≈ 9.8 m/s²)
The principle of flotation states that a floating object displaces a weight of fluid equal to:
Its own volume
Half its own weight
The weight of the container
Its own weight
Blood flows from the aorta (large radius) into many smaller arteries. For the total flow rate to remain constant, the speed of the blood in the smaller arteries is:
Faster than in the aorta
Slower than in the aorta
The same as in the aorta
Zero
Bernoulli's equation (P + (1/2)ρv² + ρgh = constant) is an expression of:
Mass conservation per unit volume
Energy conservation per unit volume
Momentum conservation per unit volume
Force conservation per unit volume
A spinning baseball curves in the air (a curveball). This is an example of the Magnus effect, which is explained by Bernoulli's principle. The ball curves because:
The spin increases the ball's weight
Pressure is higher where spin opposes airflow
The spin makes one side of the ball heavier than the other
The air has zero viscosity, allowing the ball to curve
For a horizontal pipe of varying cross-section, Bernoulli's equation simplifies to P + (1/2)ρv² = constant. Why is the ρgh term not present?
Gravity is ignored in fluid dynamics
The fluid is assumed to be massless
The pipe is horizontal, so the height (h) is constant
The pressure is constant in a horizontal pipe
Substances that undergo significant plastic deformation before they break, such as copper, are known as:
Brittle substances
Elastic substances
Ductile substances
Amorphous substances
A hot-air balloon rises because:
The balloon's fabric is lighter than air
Its total weight is less than the weight of the air it displaces.
The pressure inside the balloon is greater than the pressure outside
Heating the air removes its mass
What happens to the coefficient of viscosity of a liquid as its temperature increases?
It increases
It decreases
It remains constant
It becomes zero
What happens to the coefficient of viscosity of a gas as its temperature increases?
It increases
It decreases
It remains constant
It becomes zero
In Searle's apparatus for determining Young's modulus, a reference wire is used alongside the test wire. What is the primary purpose of this reference wire?
To double the amount of extension measured
To compensate for changes in temperature
To hold the micrometer screw gauge
To ensure the support is strong enough
Which of these materials would be considered brittle?
Lead
High-carbon steel
Wrought iron
Polythene
The flow rate of a fluid is given as 2 m³/s through a pipe with a cross-sectional area of 0.5 m². What is the velocity of the fluid?
1 m/s
2.5 m/s
4 m/s
0.25 m/s
Why does smoke from an incense stick rise in a smooth, laminar flow at first, but then become chaotic and turbulent farther up?
Smoke cools and gets denser
Speed increases, causing turbulence
Air becomes less viscous higher up
Gravity has less effect on it as it rises
A water tank has a small hole 5 m below the surface. Using Torricelli's theorem, what is the exit speed of the water? (Use g ≈ 9.8 m/s²)
49 m/s
9.9 m/s
7 m/s
2.2 m/s
Why is it dangerous to stand too close to a fast-moving train?
The train creates a high-pressure zone that pushes you away.
The fast-moving air creates low pressure pushing you towards the train.
The wind generated by the train can be strong enough to blow you over.
The ground vibrates, causing you to lose your balance.
If a fluid is incompressible, it means that its ________ is constant.
Velocity
Pressure
Density
Viscosity
In the derivation of Bernoulli's equation, what form of energy is represented by the term P (pressure)?
Kinetic Energy
Work done by the fluid per unit volume
Gravitational Potential Energy
Internal Thermal Energy
Which of the following describes plastic deformation?
A material that returns to its original shape when a force is removed.
A material that breaks immediately when force is applied.
A permanent change in shape that remains after the deforming force is removed.
A deformation that is directly proportional to the applied force.
An ideal flow of a fluid must satisfy:
Bernoulli's equation
The equation of continuity
Both Bernoulli's and continuity equations
Stokes' Law
The lift force experienced by an airplane wing is primarily due to:
The viscosity of the air
The density of the air
The pressure difference above and below wing
The gravitational force acting on the air
If a stone is submerged in water and weighs less than it does in air, this phenomenon is due to:
A reduction of the stone's mass in water
An increase in the density of water
The buoyant force acting upwards
The gravitational force acting upward
Which of the following is a polymer solid?
Glass
Sodium Chloride
Copper
Wool
The effect of a decrease of pressure with an increase in the speed of a fluid in a horizontal pipe is called:
Torricelli's effect
Bernoulli's effect
Venturi's effect
Doppler's effect
A Venturi mask, used in the medical field to deliver a known oxygen concentration, operates based on:
Archimedes' principle
Pascal's law
Bernoulli's principle
Newton's third law
Shear stress is a type of stress that causes a change in the ________ of a body.
Young's modulus has the same SI unit as which other quantity?
Which of the following is the most elastic?
If the radius of a pipe is halved, to keep the flow rate constant, the velocity of the fluid must:
Be halved
Increase by a factor of 2
Increase by a factor of 4
Remain the same
The term 'efflux' refers to:
The pressure at the bottom of a container.
The flowing out of a fluid from a container.
The buoyant force on an object.
The mixing of two different fluids.
A solid sphere has a mass 'm' and radius 'r'. Its terminal velocity in a fluid is 'v'. If a sphere of the same material has a mass of '8m', what is its radius?
What is the primary reason race cars have inverted wing-shaped spoilers?
To reduce the overall weight of the car.
To create a downward force to increase traction.
To make the car more streamlined and reduce drag.
To protect the driver in case of a rollover.
Real fluids differ from ideal fluids because real fluids have:
Mass and density
Viscosity and are compressible
The ability to flow
Potential and kinetic energy
A force of 10 N stretches a spring by 0.05 m. What is the spring constant (k)?
0.5 N/m
200 N/m
50 N/m
2 N/m
When a fluid flows through a horizontal pipe, the pressure is lowest where the fluid's speed is:
Highest
Lowest
Constant
Zero
The study of fluids in motion is called:
Fluid Statics
Fluid Dynamics
Thermodynamics
Solid-state Physics
Which instrument is used to measure the diameter of a thin wire accurately in an experiment to find Young's Modulus?
Meter rule
Vernier caliper
Screw gauge
Spirit level
The ultimate tensile strength (UTS) of a material represents the:
Stress at which the material returns to its original shape.
Stress at which the material breaks.
Maximum stress the material can withstand before starting to weaken.
Point where stress is no longer proportional to strain.
A streamline is a line or curve that is everywhere _______ to the velocity vector of the fluid flow.
Perpendicular
Tangent
Parallel
Equal
The drag force on an object moving through a fluid depends on all of the following EXCEPT:
The object's speed
The object's shape and size
The fluid's viscosity and density
The object's mass
Two raindrops are falling at their respective terminal velocities. Raindrop A has a larger radius than raindrop B. Which statement is true?
Raindrop A has a higher terminal velocity.
Raindrop B has a higher terminal velocity.
Both have the same terminal velocity.
Neither reaches a terminal velocity.
Which of these devices does NOT rely on Bernoulli's principle?
Hydraulic Brakes
Airplane Lift
Venturi Meter
Paint Sprayer
In a solid, cohesive forces are the intermolecular forces that:
Hold the solid to the walls of its container.
Bind similar molecules to one another.
Cause the solid to flow like a liquid.
Are only present in crystalline solids.
A wire of length L and radius r is stretched by a force F, causing an extension ΔL. If a wire of the same material has length 2L and radius 2r, what force is needed to cause the same extension ΔL?
The steady, non-viscous, and incompressible flow of a fluid is a description of:
Turbulent flow
Real fluid flow
Ideal fluid flow
Superfluid flow
A cylindrical pipe has a fluid flowing through it. If the pipe narrows, what happens to the streamlines?
They move farther apart.
They become more crowded together.
They stop.
They remain equally spaced.
The constant 'A' in the general form of Stokes' Law (F = Aηrv) was experimentally determined to be:
When you hold a piece of paper under your bottom lip and blow over the top, the paper rises. This demonstrates:
The Coanda effect.
The Bernoulli effect.
The Archimedes effect.
The Magnus effect.
The term for the constant, maximum velocity attained by an object falling through a resistive medium is:
Escape velocity
Critical velocity
Terminal velocity
Instantaneous velocity
The unit 'poise' is used to measure:
Pressure
Viscosity
Density
Strain
A solid material's ability to be hammered or pressed into shape without breaking is called:
Ductility
Malleability
Hardness
Brittleness
The expression for strain energy, Eₚ = (1/2)kx², is mathematically identical to what other physical quantity?
The work done in stretching the spring.
The kinetic energy of the spring.
The gravitational potential energy of the spring.
The power applied to the spring.
The pressure at a certain depth in a static fluid depends on the depth, the acceleration due to gravity, and the fluid's:
Volume
Viscosity
Density
Shape of the container
In the term (1/2)ρv² from Bernoulli's equation, ρ is the density of the fluid. What does the entire term represent?
Kinetic energy
Kinetic energy per unit volume
Momentum per unit volume
Dynamic force
When water falls from a tap, the stream narrows as it descends. This is a visual demonstration of:
Bernoulli's Principle
The Equation of Continuity
Surface Tension
Viscosity
The 'swing' of a cricket ball or the 'curve' of a baseball is largely due to:
The ball's weight
The Magnus effect, an application of Bernoulli's principle
The conservation of momentum
The Earth's rotation (Coriolis effect)
For a falling spherical object, the net force is given by Fₙₑₜ = Weight - Drag Force. What is the net force when the object reaches terminal velocity?
Equal to the weight
Equal to the drag force
Zero
Greater than the weight
Which of these devices does NOT rely on creating a low-pressure zone through high-speed fluid flow?
Atomizer
Filter Pump
Engine Carburetor
Barometer
A material has a Young's Modulus of 200 × 10⁹ Pa and is subjected to a stress of 4 × 10⁸ Pa. What is the strain in the material?
The structure of polymeric solids like plastics is best described as:
Perfectly ordered and crystalline
Completely disordered and amorphous
Intermediate between ordered and disordered
A liquid with very high viscosity
An object will float if its average density is _______ the density of the fluid it is in.
Greater than
Equal to
Less than
Independent of
A chimney works best on a windy day because the wind blowing across the top opening:
Increases the pressure at the top, pushing the smoke down.
Reduces the pressure at the top, helping to draw the smoke up.
Blocks the opening, trapping the smoke inside.
Cools the smoke, making it denser and harder to draw up.
Which term describes a fluid flow that is irregular, unsteady, and changes abruptly?
Laminar
Streamline
Turbulent
Incompressible
The equation vₜ = (2ρgr²)/(9η) shows that terminal velocity is inversely proportional to which quantity?
The density of the object (ρ)
The square of the radius (r²)
The acceleration due to gravity (g)
The viscosity of the fluid (η)
Other Physics Topics MCQs
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