Class 9th · Physics · Chapter 6
Chapter 6: Mechanical Properties of Matter
Chapter 6 of the Punjab Board Class 9th Physics textbook runs from page 127 to 147 and covers 7 topics. Its exercise has multiple choice questions, short / constructed response questions, comprehensive questions and numerical problems. Open any of those pages in GenZ Books, tap a question, and the answer is worked from this chapter.
Open Chapter 6 of Physics in GenZ Books
The same Class 9th textbook, page for page. Tap any question and get the answer worked from that chapter — English and Urdu.
What you will learn
- illustrate that forces may produce a٭ change in size and shape of an object. Define and calculate the spring constant٭ [apply the equation, spring constant = force/extension k = F/x to solve problems involving simple springs] * Sketch, plot and interpret load—extension graphs for an elastic solid and describe the associated experimental procedures. 4 * Define and use the term ‘limit of proportionality’ for_a load-extension graph [Including identifying this point an the graph (an understandingof the elastic limit is notrequired)]
- Illustrate the applications of Hooke's law [Such as that it is the fundamental principle٭ behind engineering many measurement instruments such as the spring scale, the galvanometer, and the balance wheel ofthe mechanical clock.] Define and calculate density. 00٭ Define and calculate pressure [As“force per unit area
- Use the equation pressure =٭ force/areaP= F/A to solve simple problems] Describe how pressure varies: with force and area in the context of everyday examples٭ + Describe how pressure ai/a surface produces a force in a direction at right angles to the surface [can make re
Topics in this chapter
- 6.1Deformation of Solidsp. 128
- 6.2Hooke’s Lawp. 128
- 6.3Density Insidep. 130
- 6.4Pressurep. 132
- 6.5Pressure in Liquidsp. 133
- 6.8Measurement of Pressure by Manometerp. 138
- 6.9Pascal's Lawp. 139
Exercise
- Multiple Choice Questionsp. 143
- Short / Constructed Response Questionsp. 144
- Comprehensive Questionsp. 145
- Numerical Problemsp. 146
A sample answer from GenZ Books
Explain · page 128: Ifa force Fis 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, Frese F لگ we (6.1) or F=kx or ےک
When you push or pull on a spring, the stretch or squeeze you get depends completely on how hard you pull or push. This relationship is a fundamental rule in physics that tells us how elastic objects respond to external forces.
- Direct Proportion ($F \propto x$): As you increase the applied force ($F$), the extension or compression ($x$) increases by the exact same factor, provided you do not go past the limit of proportionality.
- The Equation ($F = kx$): We turn this proportionality into an equation by introducing the spring constant [سپرنگ کانسٹنٹ], which gives us $F = kx$.
- Spring Constant ($k = \frac{F}{x}$): Rearranging the formula gives $k = \frac{F}{x}$, which measures the stiffness of the spring with SI units of $\text{N m}^{-1}$.
Think of the hanging spring balance (mechanical scale) used by a vegetable vendor in the local bazaar in Pakistan to weigh potatoes: when heavier items are hung from the hook, the applied force ($F$) increases, causing a larger extension ($x$) of the internal spring so the pointer moves proportionally down the scale.
The most common mistake you might make is forgetting that $x$ represents the change in length (extension or compression from the original resting length), not the total stretched length of the spring.
Hooke's Law is the secret behind why mechanical measurement tools work so predictably.
In short: Hooke's Law states that the force applied to a spring is directly proportional to its extension or compression within the elastic limit, written mathematically as $F = kx$.
AI-generated from the chapter text by GenZ Books. It can make mistakes — check it against your textbook and your teacher.