Mechanical Properties of FluidsNEET MCQs with solutions
Mechanical Properties of Fluids covers pressure, Pascal's law, Archimedes' principle, Bernoulli's theorem, viscosity, Stokes' law, surface tension and capillarity. NEET tests Bernoulli's equation application, buoyancy problems, surface tension and viscosity — a mix of conceptual and numerical questions.
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- 11 Physics
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- 413 questions
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Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Pressure in Fluids
A liquid exerts pressure at a point primarily because of:
Not quite — the answer is C.
Hydrostatic pressure arises from the weight of the liquid above the point, given by P = ρgh. Molecular collisions cause gas pressure, not hydrostatic pressure. Atmospheric pressure is external and separate.
Q2Pressure in Fluids
The SI unit of pressure is Pascal (Pa). Which of the following correctly expresses 1 Pa in SI base units?
Not quite — the answer is A.
Pa = N m⁻² = (kg m s⁻²) m⁻² = kg m⁻¹ s⁻². Option D is the unit of force (Newton), not pressure. Options B and C are dimensionally incorrect for pressure.
Q3Streamline Flow and Equation of Continuity
Flow in which every fluid particle follows a definite smooth path and no two paths intersect is called:
Not quite — the answer is D.
In streamline flow, each fluid particle follows a fixed smooth path called a streamline. Paths never intersect because velocity at every point is unique. Turbulent flow has irregular, crossing paths with eddies.
Q4Streamline Flow and Equation of Continuity
The SI unit of volume flow rate (discharge) is:
Not quite — the answer is C.
Volume flow rate Q = Av has dimensions [m²][m s⁻¹] = m³ s⁻¹. Option A (m² s⁻¹) is the unit of kinematic viscosity — a common confusion. Option B is speed, not flow rate.
Q5Reynolds Number and Types of Flow
Flow in which fluid particles move in smooth parallel layers without mixing with adjacent layers is called:
Not quite — the answer is A.
Laminar flow has smooth parallel layers where particles follow definite paths without mixing. It occurs at low Reynolds numbers (Re < 2000). Turbulent flow, not laminar, involves mixing and eddies.
Q6Reynolds Number and Types of Flow
Reynolds number is best described as:
Not quite — the answer is C.
Re = ρvD/η is dimensionless — no units or dimensions. It predicts laminar, transitional, or turbulent flow. Option A is wrong; Re is a ratio of forces, not a force itself.
Q7Angle of Contact & Capillarity
The angle of contact is the angle between the tangent to the liquid surface at the point of contact and the solid surface, measured through the:
Not quite — the answer is B.
The angle of contact is always measured through the liquid — between the tangent to the liquid surface at the contact point and the solid surface. Measuring through air or solid gives a different and physically meaningless angle.
Q8Angle of Contact & Capillarity
For pure water in a clean glass tube, the angle of contact is approximately:
Not quite — the answer is C.
Water strongly wets clean glass because adhesive forces between water and glass exceed cohesive forces within water. This produces a nearly zero angle of contact and a strongly concave meniscus.
Q9Viscosity
Viscosity is the property of a fluid by virtue of which it resists:
Not quite — the answer is B.
Viscosity is the internal friction between adjacent fluid layers that opposes their relative sliding motion. It is not related to compression, volume change, or temperature change directly.
Q10Viscosity
The SI unit of coefficient of viscosity η is:
Not quite — the answer is C.
The SI unit of η is Pascal-second (Pa·s), equivalent to kg m⁻¹ s⁻¹. N s is the unit of impulse (momentum), not viscosity — a common confusion in unit-based questions.
Q11Stokes' Law and Terminal Velocity
Stokes' law is valid only when the Reynolds number of the flow around the sphere is:
Not quite — the answer is D.
Stokes' law assumes creeping (laminar) flow where inertial forces are negligible. This requires Re << 1. At higher Re, inertial effects become significant and Stokes' law breaks down.
Q12Stokes' Law and Terminal Velocity
The SI unit of the coefficient of viscosity η appearing in Stokes' law F = 6πηrv is:
Not quite — the answer is C.
From F = 6πηrv, η = F/(6πrv). Units: N/(m × m s⁻¹) = N m⁻² s = Pa·s = kg m⁻¹ s⁻¹. Option D (N m⁻²) is the unit of pressure, not viscosity — a common confusion.
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Get RankUp on Google PlayQ13Surface Tension
Surface tension is defined as the force acting per unit:
Not quite — the answer is A.
Surface tension T = F/l is the tangential force per unit length along an imaginary line on the free surface. Its SI unit is N m⁻¹, equivalent to J m⁻².
Q14Surface Tension
When a glass surface is in contact with water, the angle of contact is acute (less than 90°). Which of the following correctly explains this?
Not quite — the answer is B.
When adhesive force (water-glass) exceeds cohesive force (water-water), water wets glass and the meniscus is concave — angle of contact is acute. For mercury on glass the reverse holds, giving obtuse angle.
Q15Bernoulli's Principle
Bernoulli's theorem is based on conservation of:
Not quite — the answer is C.
Bernoulli's equation is derived by applying conservation of mechanical energy to a steady, incompressible, non-viscous fluid along a streamline. Momentum and mass conservation are separate principles.
Q16Bernoulli's Principle
One essential assumption for Bernoulli's equation to be valid is that the fluid must be:
Not quite — the answer is A.
Bernoulli's theorem requires the fluid to be ideal: non-viscous, incompressible, in steady streamline flow. Viscosity causes energy dissipation, directly violating the constant-energy condition.
Q17Excess Pressure
The excess pressure inside a liquid drop of radius R and surface tension T is:
Not quite — the answer is A.
A liquid drop has one free surface. Young-Laplace equation gives ΔP = 2T/R. Option C (4T/R) is the soap bubble formula — a common substitution error.
Q18Excess Pressure
The excess pressure inside a soap bubble of radius R and surface tension T is:
Not quite — the answer is D.
A soap bubble has two free surfaces. Surface tension acts on both, giving ΔP = 2 × (2T/R) = 4T/R. Option B is the liquid drop formula — the most common error.
Q19Grand Test
A Venturimeter is primarily used to measure:
Not quite — the answer is B.
A Venturimeter applies Bernoulli's theorem and continuity equation. The pressure difference between the wide and narrow sections is used to calculate volumetric discharge. Pressure difference is a means, not the end measurement.
Q20Grand Test
A soap bubble has radius 2 cm and surface tension 0.04 N m⁻¹. The excess pressure inside the bubble is:
Not quite — the answer is A.
A soap bubble has two free surfaces, so ΔP = 4T/R = (4 × 0.04)/0.02 = 8 Pa. Option C arises from mistakenly using ΔP = 8T/R; Option B from using 2T/R (valid for a drop, not a bubble).
Q21NCERT Hidden Facts, PYQs and Integrated Concepts
An ideal fluid is assumed to be:
Not quite — the answer is A.
NCERT defines ideal fluid as incompressible and non-viscous; these assumptions underlie Bernoulli's equation derivation. Compressible or viscous fluids require different equations of motion.
Q22NCERT Hidden Facts, PYQs and Integrated Concepts
Bernoulli's equation is valid only:
Not quite — the answer is C.
Bernoulli's theorem applies along a streamline for steady, incompressible, non-viscous flow. Turbulent flow and real viscous fluids violate these assumptions.
Q23Pressure in Fluids
The hydrostatic pressure at depth h in a liquid of density ρ is P = ρgh. If depth is doubled and density is halved, the new pressure is:
Not quite — the answer is D.
New pressure = (ρ/2) × g × (2h) = ρgh = P. Doubling depth and halving density cancel exactly. A common error is to add effects rather than multiply, giving 2P incorrectly.
Q24Pressure in Fluids
In a static liquid, pressure at all points on the same horizontal level is equal. If pressure were different at two points on the same horizontal level, what would happen?
Not quite — the answer is A.
A pressure difference at the same horizontal level drives fluid flow. The fluid accelerates toward the low-pressure region until hydrostatic equilibrium is restored. Density and temperature changes do not compensate for pressure differences in incompressible fluids.
ELITE question · AIR under 50 level
This chapter has 147 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appKey Fluid Concepts
Quick revision: most questions in this chapter test these facts.
| Concept | Key Fact |
|---|---|
| Pascal's law | Pressure applied to enclosed fluid is transmitted equally in all directions |
| Archimedes' principle | Buoyant force = weight of displaced fluid; floats if ρ_body < ρ_fluid |
| Bernoulli's theorem | P + ½ρv² + ρgh = constant along a streamline |
| Stokes' law | F = 6πηrv; terminal velocity v_t = 2r²(ρ−σ)g/9η |
| Surface tension | T = F/L; excess pressure: sphere = 2T/R, bubble = 4T/R (two surfaces) |
| Capillarity | h = 2T cosθ / ρgr; rises in narrow tube if θ < 90° (water in glass) |
What the app covers in this chapter
413 questions in total, each with a detailed explanation.
| Pressure in Fluids | 58 |
| Streamline Flow and Equation of Continuity | 40 |
| Reynolds Number and Types of Flow | 40 |
| Angle of Contact & Capillarity | 39 |
| Viscosity | 38 |
| Stokes' Law and Terminal Velocity | 38 |
| Surface Tension | 38 |
| Bernoulli's Principle | 37 |
| Excess Pressure | 37 |
| Grand Test | 29 |
| NCERT Hidden Facts, PYQs and Integrated Concepts | 19 |
Questions students ask
Is Mechanical Properties of Fluids important for NEET?
Yes — Bernoulli's theorem, Archimedes' principle, surface tension and viscosity questions appear regularly. Both conceptual and numerical.
Which topics should I revise first?
Focus on Bernoulli's equation applications (Venturi, lift), Archimedes' principle and buoyancy, terminal velocity using Stokes' law, excess pressure in drops/bubbles, and capillary rise formula.
How many questions from this chapter are on RankUp?
The RankUp app has 413 questions on Mechanical Properties of Fluids, including 147 ELITE questions. Every question has a detailed explanation.
