📘 Chapter 6: Mechanical Properties of Matter – Exercise Short Answer Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This section covers exercise short answer questions from Chapter 6 Mechanical Properties of Matter including Elasticity, Pressure, Hooke's Law, Pascal's Law, and Barometer. Each question is presented with a detailed answer as per the official PECTAA 2026 Physics curriculum. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 6: Mechanical Properties of Matter
📋 Exercise Short Qs
📝 Short Qs
📖 Comprehensive Qs
🔢 Numerical Problems
✅ MCQs
✏️ Constructed Response
Mechanical Properties of Matter covers elasticity, pressure, Hooke's law, Pascal's law, and atmospheric pressure.
📖 Exercise Short Answer Questions & Answers (PECTAA 2026)
6.1 Why heavy animals like an elephant have a large area of the foot?
Answer:
Heavy animals like elephant have thick legs and large flat feet so that due to large contact area, pressure becomes less otherwise, their bones would not tolerate the pressure.
\[ P = \frac{F}{A} \]
✅ Large area → less pressure → protects bones
6.2 Why animals like deer who run fast have a small area of the foot?
Answer:
Animals like deer have a small area of the foot to increase the pressure exerted on the ground \(\left(P = \frac{F}{A}\right)\). This high pressure provides a stronger grip on the surface, preventing them from slipping and enabling them to push off quickly to run fast.
\[ P = \frac{F}{A} \]
✅ Small area → high pressure → better grip for running fast
6.3 Why is it painful to walk bare footed on pebbles?
Answer:
When we walk on pebbles, the contact area is reduced. Then the pressure due to reaction force becomes so high that it becomes painful.
\[ P = \frac{F}{A} \]
✅ Small contact area → high pressure → painful
6.4 State Pascal's law. Give an application of Pascal's law.
Answer:
Pascal's Law: When pressure is applied at one point in an enclosed fluid, it is transmitted equally to all parts of fluid without loss.
Application: The technology of hydraulic systems is based on Pascal's law. Some useful hydraulic systems are:
- (i) Hydraulic press
- (ii) Car lift at service stations
- (iii) Hydraulic brakes of vehicles
✅ Pressure transmitted equally in all directions
6.5 State what do you mean by elasticity of a solid.
Answer:
An object is said to be elastic, if after removal of the deforming force, it restores to its original size and shape. This property of the material is known as elasticity.
✅ Elasticity → ability to regain original shape after deforming force is removed
6.6 What is Hooke's law? Does an object remain elastic beyond elastic limit? Give reason.
Answer:
Hooke's Law: If a force \(F\) is applied on a spring to stretch or compress it, the extension or compression \(x\) has been found directly proportional to the applied force within the elastic limit. Thus,
\[ F \propto x \]
Beyond Elastic Limit: No. Beyond the elastic limit, the change becomes permanent. The object or material does not regain its original shape or size even after the removal of the deforming force.
✅ Hooke's Law: \(F \propto x\) (within elastic limit)
6.7 Distinguish between force and pressure.
Answer:
| Force | Pressure |
|---|---|
| A force is a push or pull that can start, stop, or change the magnitude and direction of a body's velocity. | Pressure is defined as the force exerted normally on unit area of an object. |
| It is measured in newtons (N). | It is measured in pascals (Pa). |
| Formula: \(F = ma\) | Formula: \(P = \frac{F}{A}\) |
✅ Force (N) vs Pressure (Pa = N/m²)
6.8 What is the relationship between liquid pressure and the depth of the liquid?
Answer:
Liquid pressure is directly proportional to the depth of the liquid, given by the formula:
\[ P = \rho gh \]
This shows that liquid pressure increases with depth (\(P \propto h\)).
✅ \(P = \rho gh\) → Pressure increases with depth
6.9 What is the basic principle to measure atmospheric pressure by a simple mercury barometer?
Answer:
The basic principle is that atmospheric pressure is measured by the height of the mercury column it can support.
The pressure inside the mercury column at the dish level equals the atmospheric pressure acting on the surface of the mercury.
\[ P = \rho gh \]
✅ Atmospheric pressure = height of mercury column × density × g
6.10 State the basic principle used in the hydraulic brake system of automobiles.
Answer:
The brakes of some vehicles work on Pascal's law.
When pedal is pushed down, the piston applies pressure on the liquid in the master cylinder. The liquid pressure is transmitted equally to all the larger pistons of other cylinders.
✅ Hydraulic brakes work on Pascal's law
📐 Key Concepts – Mechanical Properties of Matter (Exercise Short Questions)
Pressure: \(P = \frac{F}{A}\)
Liquid Pressure: \(P = \rho gh\)
Hooke's Law: \(F \propto x\)
Pascal's Law: Pressure transmitted equally in all directions
Barometer Principle: \(P = \rho gh\)
💡 Exam Tip:
For exercise short questions, write concise and accurate answers. Use definitions, formulas, and examples where required. These questions test your understanding of fundamental concepts like elasticity, pressure, Hooke's law, Pascal's law, and barometer. These questions follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Chapter 1Physical Quantities and Measurements
Chapter 2Kinematics
Chapter 3Dynamics
Chapter 4Turning Effect of Forces
Chapter 5Work and Energy
Chapter 6✨ Mechanical Properties of Matter
Chapter 7Thermal Properties of Matter
Chapter 8Magnetism
Chapter 9Nature of Science
📖 Complete syllabus coverage for Class 9 Physics (PECTAA 2026) – Chapters 1 to 9
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus