NEET PhysicsUpdated 19 Oct 2026

Mechanical Properties of Fluids: NEET PYQs and weightage

Mechanical Properties of Fluids carries 2.9 of 100 Physics marks in NEET by past-paper share: 22 of the 758 tagged NEET Physics PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 17 of 30 Physics chapters.

Take the 25-question Mechanical Properties of Fluids test Formula sheet ↓All NEET Physics chapters

2.9/100 Weight in Physics

Exam importance (3/5, by past-paper share)

22 NEET PYQs

392 Practice questions

361 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Physics PYQs in the bank (22 of 758), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

Mechanical Properties of Fluids: formula sheet for NEET

14 formulas, each with when to use it. Copy it onto one page of your notebook: that page is this chapter's handbook.

Bernoulli's equation
$P + \frac{1}{2} ρ v^{2} + ρ g h = constant (along a streamline)$
Use it when: an ideal fluid flows steadily and speed or height changes between two points
Equation of continuity
$A_{1} v_{1} = A_{2} v_{2} (A v = volume flow rate, m^{3} /s)$
Use it when: a pipe narrows or widens, or one tube splits into many holes (add up all the hole areas)
Pressure at depth
$P = P_{a} + ρ g h$
$P - P_{a} = ρ g h (gauge pressure)$
Use it when: a liquid is at rest and you need the pressure $h$ below the open surface
Torricelli's law
$v = 2 g h (h measured down from the liquid surface to the hole)$
Use it when: liquid flows out of a small hole in a wide tank that is open at the top
Archimedes' principle
$B = ρ_{fluid} V_{submerged} g (B = buoyant force)$
Use it when: a body floats or is immersed, or you are finding apparent weight
Terminal velocity
$v_{t} = \frac{2 a ^{2} ( ρ - σ ) g}{9 η} (ρ = density of the sphere, σ = density of the fluid)$
Use it when: a sphere falls at constant speed through a viscous fluid ( $v_{t} \propto a^{2}$ )
Stokes' law
$F = 6 π η a v$
Use it when: you need the viscous drag on a sphere of radius $a$ moving at speed $v$
Capillary rise
$h = \frac{2 S cos θ}{ρ g a} (a = radius of the tube)$
Use it when: a liquid rises in a thin tube (if $θ > 9 0^{\circ}$ , as with mercury, the liquid falls instead)
Excess pressure in a drop
$P_{i} - P_{o} = \frac{2 S}{r}$
Use it when: you have a liquid drop, or an air bubble inside a liquid (one surface)
Excess pressure in a soap bubble
$P_{i} - P_{o} = \frac{4 S}{r}$
Use it when: a bubble in air has two surfaces (soap film)
Coefficient of viscosity
$η = \frac{F / A}{v / l} (SI unit Pa s = N s m^{- 2})$
Use it when: a plate slides at speed $v$ over a liquid layer of thickness $l$
Hydraulic lift
$F_{2} = F_{1} \times \frac{A _{2}}{A _{1}}$
$A_{1} L_{1} = A_{2} L_{2} (piston movements)$
Use it when: Pascal's law carries pressure from a small piston to a large one
Surface tension of a film
$S = \frac{F}{2 l}$
Use it when: a slider of length $l$ holds a soap film, which has two surfaces
Dynamic lift
$Δ P = \frac{1}{2} ρ (v_{2}^{2} - v_{1}^{2})$
$lift = Δ P \times A$
Use it when: air moves faster over the top of a wing than under it (ignore the height difference)

Trap

Count the surfaces before you write the excess pressure. A soap bubble in air has two surfaces, so use 4S/r. An air bubble inside water has only one surface, so use 2S/r, the same as a drop. Mixing these up doubles or halves the answer. Also note that 1 atm = 1.013 × 10⁵ Pa, not 10⁵ Pa.

How does NEET ask Mechanical Properties of Fluids?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1PhysicsNEET UG PYQSurface Tension

Try right here · No sign-in

A balloon is made of a material of surface tension S and its inflation outlet (from where gas is filled in it) has small area A. It is filled with a gas of density

ρ

and takes a spherical shape of radius R. When the gas is allowed to flow freely out of it, its radius r changes from R to 0 (zero) in time T. If the speed

v (r)

of gas coming out of the balloon depends on r as

r^{a}

and

T \propto S^{α} A^{β} ρ^{γ} R^{δ}

then

Answer key (A) & worked solution

Correct answer: Option A

T \propto S^{α} A^{β} ρ^{r} R^{δ}

[T] = [M T^{- 2}]^{α} [L^{2}]^{β} [M L^{- 3}]^{γ} [L^{δ}]

[T] = [M^{α + γ} L^{2 β - 3 γ + δ} T^{- 2 α}]

Company powers

- 2 α = 1 .... (1) \Rightarrow α = - \frac{1}{2}

α + γ = 0 .. (2) \Rightarrow γ = \frac{1}{2}

2 β - 3 γ + δ = 0 .... (3)

2 β - \frac{3}{2} + δ = 0

2 β = \frac{3}{2} - δ

δ = \frac{7}{2}

2 β = \frac{3}{2} - \frac{7}{2} = \frac{- 4}{2} = - 2

β = - 1

a = - \frac{1}{2}, α = - \frac{1}{2}, β = - 1, γ = - \frac{1}{2}, δ = \frac{7}{2}

Q2PhysicsNEET UG PYQPressure and Density

A submarine is designed to withstand an absolute pressure of 100 atm . How deep can it go below the water surface? (Consider the density of water

= 1000 kg m^{- 3}

1 atm = 1 \times 1 0^{5} Pa

and gravitational acceleration

g = 10 m / s^{2}

)

A9900 m

B99 m

C9000 m

D990 m

Answer key (D) & worked solution

Correct answer: Option D

P = P_{0} + ρ g h

\Rightarrow 100 \times 1 0^{5} = 1 0^{5} + 1 0^{3} \times 10 \times h

\Rightarrow 1 0^{7} = 1 0^{5} + 1 0^{4} h

\Rightarrow 1 0^{3} = 10 + h

\Rightarrow h = 1000 - 10 = 990 m

Q3PhysicsNEET UG PYQSurface Tension

A certain number of spherical drops of a liquid of radius ‘r’ coalesce to form a single drop of radius ‘R’ and volume ‘V’. If ‘T’ is the surface tension of the liquid, then

AEnergy = 3VT

(\frac{1}{r} - \frac{1}{R})

is released

BEnergy is neither released nor absorbed

CEnergy = 4VT

(\frac{1}{r} - \frac{1}{R})

is released

DEnergy = 3VT

(\frac{1}{r} + \frac{1}{R})

is absorbed

Answer key (A) & worked solution

Correct answer: Option A

S E_{i} = T 4 π^{2} n = T (\frac{3 V}{r}) S E_{f} = T 4 π R^{2} = T \frac{3 V}{R} Δ E = S E_{f} - S E_{i} = T 3 V (\frac{1}{R} - \frac{1}{r}) = 3 T V [\frac{1}{R} - \frac{1}{r}] This amount of energy is released

Q4PhysicsNEET UG PYQSurface Tension

The amount of energy required to form a soap bubble of radius 2 cm from a soap solution is nearly: (surface tension of soap solution = 0.03 Nm

^{- 1}

)

5.06 \times 1 0^{- 4} J

3.01 \times 1 0^{- 4} J

50.1 \times 1 0^{- 4} J

30.16 \times 1 0^{- 4} J

Answer key (B) & worked solution

Correct answer: Option B

E = 2 T (4 π R^{2})

$\begin{gathered} = 2\left( {0.03} \right)\left( 4 \right)\left( {3.14} \right){\left( {2 \times {{10}^{ - 2}}} \right)^2} \\ = 3.01 \times {10^{ - 4}}J \\ \end{gathered} $

Q5PhysicsNEET UG PYQSurface Tension

A thin flat circular disc of radius 4.5 cm is placed gently over the surface of water. If surface of water. If surface tension of water is

0.07 N m^{- 1}

, then the excess force required to take it away from the surface is:

A198 N

B1.98 mN

C99 N

D19.8 mN

Answer key (D) & worked solution

Correct answer: Option D

Excess Force

= T .2 π R

= 007 \times 2 \times \frac{22}{7} \times \frac{4.5}{100} = 19.8 m N

Q6PhysicsNEET UG PYQSurface Tension

A rectangular film of liquid is extended from (4cm × 2cm) to (5cm × 4cm). If the work done is 3 × 10

^{- 4}

J, the value of the surface tension of the liquid is

A0.125 N m

^{- 1}

B0.2 N m

^{- 1}

C8.0 N m

^{- 1}

D0.250 N m

^{- 1}

Answer key (A) & worked solution

Correct answer: Option A

W = T(2∆A)

\Rightarrow T = \frac{W}{2Δ A} = \frac{3 \times 10 ^{- 4}}{2 \times 12 \times 10 ^{- 4}} = 0.125 N m^{- 1}

Q7PhysicsNEET UG PYQSurface Tension

Three liquids of densities ρ

_{1}

, ρ

_{2}

and ρ

_{3}

(with ρ

_{1}

> ρ

_{2}

> ρ

_{3}

), having the same value of surface tension T, rise to the same height in three identical capillaries. The angles of contact θ

_{1}

, θ

_{2}

and θ

_{3}

obey

0 ⩽ θ_{1} < θ_{2} < θ_{3} < \frac{π}{2}

\frac{π}{2} < θ_{1} < θ_{2} < θ_{3} < π

π < θ_{1} < θ_{2} < θ_{3} < \frac{π}{2}

\frac{π}{2} < θ_{1} < θ_{2} < θ_{3} < 0

Answer key (A) & worked solution

Correct answer: Option A

h = \frac{2 T c o s θ}{ρ g r}

As r, h, T are same

\Rightarrow \frac{c o s θ}{ρ}

= constant

\Rightarrow \frac{c o s θ _{1}}{ρ _{1}} = \frac{c o s θ _{2}}{ρ _{2}} = \frac{c o s θ _{3}}{ρ _{3}}

ρ_{1} > ρ_{2} > ρ_{3}

\Rightarrow cos θ_{1} > cos θ_{2} > cos θ_{3}

\Rightarrow θ_{1} < θ_{2} < θ_{3}

As water rises

\Rightarrow θ

must be acute So,

0 ⩽ θ_{1} < θ_{2} < θ_{3} < \frac{π}{2}

Q8PhysicsNEET UG PYQSurface Tension

The wettability of the surface by a liquid depends primarily on

AViscosity

BSurface tension

CDensity

DAngle of contact between the surface and the liquid

Answer key (D) & worked solution

Correct answer: Option D

Wetting is the ability of a liquid to maintain contact with a solid surface and the degree of wetting is known as wettability. It depends on the angle of contact between the surface and the liquid.

Which topics in Mechanical Properties of Fluids carry the most questions?

All 6 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Surface Tension	11	115
Bernoulli's Principle and Its Applications	4	58
Viscosity	4	49
Pressure and Density	3	146
Streamline Flow	0	22
Miscellaneous Examples	0	2

Why does Mechanical Properties of Fluids show "–" until you answer 3 questions?

Unknown is not zero. Until you answer at least 3 graded questions in Mechanical Properties of Fluids, ViJEEta shows – instead of a zero or a 50% default. Book exercises can raise chapter mastery up to 0.60, adaptive practice up to 0.75, and only a timed chapter test or mock can certify 0.80 and above.

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What happens when you test Mechanical Properties of Fluids?

Every chapter test is 25 questions. It starts at moderate difficulty and adapts after each saved answer. If you open a solution before answering, that attempt earns no credit, so your mastery stays honest.

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Chapters either side of Mechanical Properties of Fluids by weight

Atoms Weight 3.0/100 Oscillations Weight 3.0/100 Nuclei Weight 2.9/100 Waves Weight 2.9/100

Mechanical Properties of Fluids: NEET PYQs and weightage

Mechanical Properties of Fluids: formula sheet for NEET

Bernoulli's equation

Equation of continuity

Pressure at depth

Torricelli's law

Archimedes' principle

Terminal velocity

Stokes' law

Capillary rise

Excess pressure in a drop

Excess pressure in a soap bubble

Coefficient of viscosity

Hydraulic lift

Surface tension of a film

Dynamic lift

How does NEET ask Mechanical Properties of Fluids?

Which topics in Mechanical Properties of Fluids carry the most questions?

Why does Mechanical Properties of Fluids show "–" until you answer 3 questions?

What happens when you test Mechanical Properties of Fluids?

Chapters either side of Mechanical Properties of Fluids by weight