Mechanical Properties of Fluids Class 11 Assertion Reason Questions Physics Chapter 9

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Last Updated on April 25, 2025 by XAM CONTENT

Hello students, we are providing assertion reason questions for class 11. Assertion Reason questions are the new question format that is introduced in CBSE board. The resources for assertion reason questions are very less. So, to help students we have created chapterwise assertion reason questions for class 11 Physics. In this article, you will find assertion reason questions for CBSE Class 11 Physics Chapter 9 Mechanical Properties of Fluids. It is a part of Assertion Reason Questions for CBSE Class 11 Physics Series.

Chapter	Mechanical Properties of Fluids
Type of Questions	Assertion Reason Questions
Nature of Questions	Competency Based Questions
Board	CBSE
Class	11
Subject	Physics
Useful for	Class 11 Studying Students
Answers provided	Yes
Difficulty level	Mentioned
Important Link	Class 11 Physics Chapterwise Assertion Reason

Assertion Reason Questions on Mechanical Properties of Fluids

Assertion Reason Questions

Directions:
Each of the following questions consists of two statements: an Assertion (A) and a Reason (R). Answer them by selecting the correct option:
(a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

Q1. Assertion (A): Pressure at a point inside a liquid is the same in all directions.
Reason (R): Pressure in a fluid at rest acts perpendicular to any surface in contact with it.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation: In a fluid at rest, pressure is isotropic (same in all directions). This is because it arises due to molecular collisions which are random. Pressure always acts normal to the surface, explaining why both statements are true and related.

Difficulty Level: Moderate

Q2. Assertion (A): A floating body displaces a volume of fluid whose weight is equal to its own weight.
Reason (R): According to Archimedes’ principle, the buoyant force equals the weight of the displaced fluid.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation: Archimedes’ principle governs floating bodies. For equilibrium (floating), the buoyant force (which is equal to the weight of displaced fluid) must balance the weight of the object. Hence, both statements are true and connected.

Difficulty Level: Moderate

Q3. Assertion (A): Viscosity is higher for gases than liquids.
Reason (R): Liquids have stronger intermolecular forces than gases.

Answer: (d) Assertion is false, but Reason is true.

Explanation: The assertion is false — viscosity is generally higher in liquids than gases. The reason is true, as liquids have stronger intermolecular forces. However, in gases, viscosity increases with temperature, unlike in liquids.

Difficulty Level: Tough

Q4. Assertion (A): Streamline flow is more stable than turbulent flow.
Reason (R): In streamline flow, each particle of the fluid follows a definite path.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation: In streamline (or laminar) flow, the paths of fluid particles do not cross, making it more stable and predictable than turbulent flow. The reason correctly explains the assertion.

Difficulty Level: Moderate

Q5. Assertion (A): The terminal velocity of a falling sphere in a viscous medium increases with radius.
Reason (R): Terminal velocity $v_t=\frac{2 r^2(\rho-\sigma) g}{9 \eta}$, where $\rho$ and $\sigma$ are densities of sphere and fluid.

Answer: (b) Both $A$ and $R$ are true, but $R$ is not the correct explanation of $A$.

Explanation: Both A and R are true: terminal velocity does increase with the square of the radius as per the formula. However, the reason, while correct in content, is a formula and does not directly explain why velocity increases with radius in terms of physical principles. Hence, (b) is the best fit.

Difficulty Level: Tough

Also check

• Waves Class 11 Assertion Reason Questions Physics Chapter 14
• Oscillations Class 11 Assertion Reason Questions Physics Chapter 13
• Kinetic Theory Class 11 Assertion Reason Questions Physics Chapter 12
• Thermodynamics Class 11 Assertion Reason Questions Physics Chapter 11
• Thermal Properties of Matter Class 11 Assertion Reason Questions Physics Chapter 10
• Mechanical Properties of Fluids Class 11 Assertion Reason Questions Physics Chapter 9
• Mechanical Properties of Solids Class 11 Assertion Reason Questions Physics Chapter 8
• Gravitation Class 11 Assertion Reason Questions Physics Chapter 7
• System of Particles and Rotational Motion Class 11 Assertion Reason Questions Physics Chapter 6
• Work, Energy, and Power Class 11 Assertion Reason Questions Physics Chapter 5
• Laws of Motion Class 11 Assertion Reason Questions Physics Chapter 4
• Motion in a Plane Class 11 Assertion Reason Questions Physics Chapter 3
• Motion in a Straight Line Class 11 Assertion Reason Questions Physics Chapter 3
• Units and Measurements Class 11 Assertion Reason Questions Physics Chapter 2

Topics from which assertion reason questions may be asked

• Pressure and Pascal’s law
• Bernoulli’s principle
• Viscosity and surface tension

Hydraulic systems use Pascal’s law to multiply force — a principle behind car brakes and lifts.

Assertion reason questions from the above given topic may be asked.

Frequently Asked Questions (FAQs) on Mechanical Properties of Fluids Assertion Reason Questions Class 11