MECHANICAL PROPERTIES OF FLUIDS-Objective Questions for Entrance Exams
The topic Mechanical Properties of Fluids – Elasticity forms a critical conceptual bridge between solid mechanics and fluid mechanics in senior secondary and competitive physics curricula. Questions from this domain consistently test a student’s understanding of bulk modulus, compressibility, volume strain, hydraulic pressure, and elastic response of fluids, which are fundamental not only to theoretical physics but also to practical applications in hydraulics, geophysics, material science, and engineering systems.
In competitive examinations such as JEE (Main & Advanced), NEET, AIIMS, BITSAT, KVPY, Olympiads, and various state engineering entrance tests, elasticity of fluids is frequently assessed through conceptual MCQs, dimensional analysis, numerical estimations, assertion–reason problems, and real-life application based questions. Mastery of this topic requires clarity in definitions, physical interpretation of formulas, and the ability to distinguish elastic behavior of solids, liquids, and gases under pressure.
The following MCQs have been carefully designed and curated in alignment with standard examination patterns, drawing inspiration from repeatedly tested concepts and historically asked questions. Each problem is accompanied by a clear explanation, ensuring conceptual reinforcement rather than rote memorization. This collection serves as a high-yield practice resource for aspirants targeting top ranks in medical and engineering entrance examinations.
Actual questions from IIT-JEE, NEET, AIIMS, BITSAT & KVPY —
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Q1
A cube of side \(a\) is subjected to a uniform hydraulic pressure \(p\). If the bulk modulus of the material is \(K\), the decrease in volume of the cube is (Exam: IIT-JEE Year: 1998)
(A) \(\dfrac{p a^3}{K}\)
(B) \(\dfrac{3 p a^3}{K}\)
(C) \(\dfrac{p a}{K}\)
(D) \(\dfrac{K a^3}{p}\)
✅ Correct: (A)
Q2
When pressure on a liquid is increased, its density (Exam: NEET (AIPMT) Year: 2003)
(A) decreases
(B) remains unchanged
(C) increases
(D) becomes zero
✅ Correct: (C)
Q3
The SI unit of bulk modulus is the same as that of (Exam: JEE Main Year: 2014)
(A) strain
(B) stress
(C) density
(D) surface tension
✅ Correct: (B)
Q4
Water is slightly compressible because (Exam: AIIMS Year: 2007)
(A) its bulk modulus is zero
(B) its bulk modulus is very small
(C) its bulk modulus is very large
(D) it has viscosity
✅ Correct: (C)
Q5
The reciprocal of bulk modulus is called (Exam: BITSAT Year: 2009)
(A) elasticity
(B) compressibility
(C) rigidity
(D) plasticity
✅ Correct: (B)
Q6
If pressure applied on a liquid is doubled, the fractional decrease in volume will (Exam: JEE Advanced Year: 2016)
(A) become half
(B) remain same
(C) become double
(D) become zero
✅ Correct: (C)
Q7
Which of the following has maximum bulk modulus? (Exam: IIT-JEE Year: 2001)
(A) Air
(B) Water
(C) Mercury
(D) Steel
✅ Correct: (D)
Q8
A liquid is said to be incompressible if its bulk modulus is (Exam: State Engg. Exam Year: 2010)
(A) zero
(B) finite
(C) negative
(D) infinite
✅ Correct: (D)
Q9
Bulk modulus depends mainly on (Exam: NEET Year: 2018)
(A) shape of container
(B) mass of liquid
(C) nature of material
(D) acceleration due to gravity
✅ Correct: (C)
Q10
The dimensional formula of bulk modulus is (Exam: IIT-JEE Year: 1995)
(A) \([M L^{-1} T^{-2}]\)
(B) \([M L T^{-2}]\)
(C) \([M L^{-2} T^{-2}]\)
(D) \([M^0 L^0 T^0]\)
✅ Correct: (A)
Q11
A decrease in volume of a body under uniform pressure is called (Exam: Olympiad Year: 2008)
(A) shear strain
(B) longitudinal strain
(C) volume strain
(D) linear strain
✅ Correct: (C)
Q12
If \(K_1 > K_2\), then (Exam: JEE Main Year: 2017)
(A) material 1 is more compressible
(B) material 2 is more compressible
(C) both equally compressible
(D) compressibility is zero
✅ Correct: (B)
Q13
For an ideal liquid, the bulk modulus is assumed to be (Exam: IIT-JEE Year: 1999)
(A) zero
(B) finite
(C) infinite
(D) negative
✅ Correct: (C)
Q14
When a liquid is subjected to pressure, its volume decreases but its shape (Exam: NEET Year: 2020)
(A) changes
(B) remains same
(C) becomes spherical
(D) becomes irregular
✅ Correct: (B)
Q15
The ratio of change in pressure to fractional change in volume is (Exam: BITSAT Year: 2012)
(A) Young’s modulus
(B) bulk modulus
(C) shear modulus
(D) Poisson’s ratio
✅ Correct: (B)
Q16
Bulk modulus is applicable to (Exam: IIT-JEE Year: 2004)
(A) solids only
(B) liquids only
(C) gases only
(D) solids, liquids and gases
✅ Correct: (D)
Q17
A gas has low bulk modulus because (Exam: NEET Year: 2015)
(A) molecules are closely packed
(B) intermolecular space is large
(C) density is high
(D) viscosity is low
✅ Correct: (B)
Q18
If pressure on a liquid is increased by \(\Delta p\), the volume strain produced is (Exam: JEE Advanced Year: 2019)
(A) \(K \Delta p\)
(B) \(\dfrac{\Delta p}{K}\)
(C) \(\dfrac{K}{\Delta p}\)
(D) zero
✅ Correct: (B)
Q19
Which is most compressible? (Exam: AIIMS Year: 2006)
(A) Solid
(B) Liquid
(C) Gas
(D) Plasma
✅ Correct: (C)
Q20
The bulk modulus of water is about (Exam: IIT-JEE Year: 2002)
(A) \(2 \times 10^3 \,\text{Pa}\)
(B) \(2 \times 10^6 \,\text{Pa}\)
(C) \(2 \times 10^9 \,\text{Pa}\)
(D) \(2 \times 10^{12} \,\text{Pa}\)
✅ Correct: (C)
Q21
Under hydraulic pressure, stress produced in a liquid is (Exam: State Engg. Exam Year: 2011)
(A) tensile
(B) shear
(C) compressive
(D) tangential
✅ Correct: (C)
Q22
Which elastic constant relates pressure with volume strain? (Exam: JEE Main Year: 2016)
(A) Young’s modulus
(B) shear modulus
(C) bulk modulus
(D) rigidity modulus
✅ Correct: (C)
Q23
If the bulk modulus of a substance is zero, it behaves like (Exam: Olympiad Year: 2010)
(A) an ideal solid
(B) an incompressible liquid
(C) a perfectly compressible medium
(D) vacuum
✅ Correct: (C)
Q24
Bulk modulus is independent of (Exam: NEET Year: 2019)
(A) pressure applied (within limits)
(B) temperature (approximately)
(C) shape of the body
(D) nature of material
✅ Correct: (C)
Q25
A given volume of liquid is compressed isothermally. The bulk modulus is defined as (Exam: IIT-JEE Year: 1997)
(A) \(-pV\)
(B) \(-V \dfrac{dp}{dV}\)
(C) \(-\dfrac{dV}{dp}\)
(D) \(\dfrac{dp}{dV}\)
✅ Correct: (B)
Q26
Which quantity has the same dimensions as bulk modulus? (Exam: BITSAT Year: 2013)
(A) Energy density
(B) Strain
(C) Momentum
(D) Angular velocity
✅ Correct: (A)
Q27
In fluids, elastic behaviour is mainly associated with (Exam: JEE Advanced Year: 2018)
(A) shear deformation
(B) volume deformation
(C) longitudinal deformation
(D) bending
✅ Correct: (B)
Q28
The compressibility of a liquid is very small because (Exam: NEET Year: 2017)
(A) density is low
(B) molecules are rigid
(C) intermolecular spacing is small
(D) viscosity is high
✅ Correct: (C)
Q29
Bulk modulus is numerically equal to (Exam: IIT-JEE Year: 2000)
(A) pressure causing unit volume strain
(B) volume causing unit pressure
(C) stress causing unit shear strain
(D) strain causing unit stress
✅ Correct: (A)
Q30
The bulk modulus of air at STP is of the order of (Exam: JEE Main Year: 2015)
(A) \(10^2\) Pa
(B) \(10^5\) Pa
(C) \(10^9\) Pa
(D) \(10^{12}\) Pa
✅ Correct: (B)
Q31
Which of the following does not affect bulk modulus? (Exam: State Engg. Exam Year: 2012)
(A) Nature of material
(B) Pressure range
(C) Temperature
(D) Shape of body
✅ Correct: (D)
Q32
A liquid under high pressure stores energy in the form of (Exam: Olympiad Year: 2011)
(A) kinetic energy
(B) elastic potential energy
(C) thermal energy
(D) surface energy
✅ Correct: (B)
Q33
Bulk modulus is a measure of (Exam: NEET Year: 2014)
(A) rigidity
(B) hardness
(C) resistance to compression
(D) resistance to shear
✅ Correct: (C)
Q34
If the pressure on a liquid is reduced, its volume (Exam: IIT-JEE Year: 1996)
(A) decreases
(B) remains same
(C) increases
(D) becomes zero
✅ Correct: (C)
Q35
In fluids, the restoring force against deformation arises due to (Exam: JEE Advanced Year: 2020)
(A) shear stress
(B) tensile stress
(C) compressive stress
(D) friction
✅ Correct: (C)
Q36
The inverse of compressibility represents (Exam: BITSAT Year: 2011)
(A) density
(B) elasticity
(C) bulk modulus
(D) pressure
✅ Correct: (C)
Q37
Which statement is correct? (Exam: NEET Year: 2016)
(A) Liquids cannot be compressed at all
(B) Liquids are perfectly elastic
(C) Liquids are slightly compressible
(D) Liquids have zero bulk modulus
✅ Correct: (C)
Q38
A fluid having very high bulk modulus behaves almost like (Exam: IIT-JEE Year: 2003)
(A) a gas
(B) a solid
(C) a vacuum
(D) plasma
✅ Correct: (B)
Q39
The bulk modulus of a substance depends on (Exam: JEE Main Year: 2019)
(A) external shape
(B) internal structure
(C) volume
(D) mass
✅ Correct: (B)
Q40
For small deformations, bulk modulus remains (Exam: IIT-JEE Year: 1994)
(A) zero
(B) negative
(C) constant
(D) infinite
✅ Correct: (C)
Q41
Which elastic property is relevant for fluids at rest? (Exam: NEET Year: 2021)
(A) Young’s modulus
(B) shear modulus
(C) bulk modulus
(D) torsional modulus
✅ Correct: (C)
Q42
A given mass of water is compressed. The work done is stored as (Exam: Olympiad Year: 2012)
(A) kinetic energy
(B) gravitational energy
(C) elastic potential energy
(D) chemical energy
✅ Correct: (C)
Q43
Bulk modulus is maximum for (Exam: State Engg. Exam Year: 2013)
(A) rubber
(B) water
(C) steel
(D) air
✅ Correct: (C)
Q44
If volume strain is zero, the bulk modulus is (Exam: IIT-JEE Year: 1993)
(A) zero
(B) finite
(C) infinite
(D) negative
✅ Correct: (C)
Q45
The elastic behaviour of fluids is analogous to (Exam: JEE Advanced Year: 2015)
(A) shear in solids
(B) stretching of wires
(C) compression of springs
(D) bending of beams
✅ Correct: (C)
Q46
Which of the following quantities is least for gases? (Exam: NEET Year: 2013)
(A) Density
(B) Bulk modulus
(C) Volume
(D) Pressure
✅ Correct: (B)
Q47
A liquid’s resistance to compression is due to (Exam: IIT-JEE Year: 2005)
(A) viscosity
(B) surface tension
(C) intermolecular forces
(D) gravity
✅ Correct: (C)
Q48
The bulk modulus of a liquid slightly (Exam: JEE Main Year: 2018)
(A) decreases with pressure
(B) increases with pressure
(C) becomes zero
(D) is independent of pressure always
✅ Correct: (B)
Q49
Which is correct regarding bulk modulus? (Exam: Olympiad Year: 2009)
(A) Scalar quantity
(B) Vector quantity
(C) Dimensionless
(D) Negative
✅ Correct: (A)
Q50
In hydraulic systems, the concept of bulk modulus is important to understand (Exam: BITSAT Year: 2014)
(A) flow rate
(B) pressure transmission and compression losses
(C) surface tension
(D) viscosity
✅ Correct: (B)
Frequently Asked Questions
Mechanical properties of fluids describe how liquids and gases respond to forces, including their ability to flow, transmit pressure, resist motion, and show surface effects like viscosity and surface tension.
A fluid is a substance that cannot resist shear stress in static condition and continuously deforms under even a small tangential force. Liquids and gases are fluids.
Pressure is the normal force exerted per unit area by a fluid on any surface in contact with it, given by P = F/A.
Pressure increases with depth according to P = P0 + ?gh, where ? is density, g is acceleration due to gravity, and h is depth.
Pascal’s law states that pressure applied to an enclosed fluid is transmitted equally and undiminished to all parts of the fluid and the container walls.
Pascal’s law is applied in hydraulic lifts, hydraulic brakes, hydraulic presses, and hydraulic jacks.
Buoyant force is the upward force exerted by a fluid on an immersed body, opposing the weight of the body.
A body immersed in a fluid experiences an upward force equal to the weight of the fluid displaced by it.
Objects float if the buoyant force equals or exceeds their weight, usually when their average density is less than the fluid density.
Viscosity is the internal resistance of a fluid to the relative motion between its layers.
The coefficient of viscosity is the force per unit area required to maintain a unit velocity gradient between two parallel layers of a fluid.
Stokes’ law states that the viscous force on a small sphere moving in a fluid is F = 6p?rv.
Terminal velocity is the constant maximum velocity attained by a body falling through a viscous fluid when net force becomes zero.
Terminal velocity is given by v = (2r²(? - s)g)/(9?).
Surface tension is the property of a liquid surface that makes it behave like a stretched elastic membrane.
MECHANICAL PROPERTIES OF FLUIDS – Learning Resources
