Have you ever observed what a rubber band does when you pull it and then immediately goes back to its former shape when you release it? This observation is the best explanation of the principles of NCERT Class 11 Physics Chapter 8 Notes Mechanical Properties of Solids. This chapter addresses the behaviour of materials under various types of forces such as tension, compression, shear and why knowledge of elasticity, stress and strain is very important in real-life engineering, such as designing bridges, skyscrapers, aeroplanes and machines.
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As a fundamental concept in the CBSE Class 11 Physics syllabus, the chapter is also indispensably relevant to both competition-based exams such as JEE, NEET and other entrance exams where questions on stress-strain relationships, Hooke's Law, Young's Modulus and elastic behaviour are regularly set. NCERT Class 11 Physics Chapter 8 Notes Mechanical Properties of Solids make difficult concepts easier to understand in the form of explanations by subject specialists. These NCERT notes include: knowledge in well-organised formulas and derivations, to be recalled in a moment, conceptual clarity, illustrations and diagrams, significant instructions and points to be noted in last-minute revision, use of practice questions and numerical problems in order to strengthen application skills. Be it your CBSE board examinations or your JEE/ NEET, these notes are the best revision guide. They not only make you well acquainted with the chapter but also help you know confidently how to address both theoretical and numerical questions.
Also, students can refer,
The NCERT Class 11 Physics Chapter 8 Notes PDF includes such important topics as stress, strain, Hooke's law, elastic moduli, and applications of elasticity in life as possible. These brief notes are simple to revise, save time and highly applicable to the CBSE board as well as competitive exams such as JEE and NEET.
NCERT Class 11 Physics Chapter 8 Notes Mechanical Properties of Solids provide a brief but clear outline of how solids react to such forces as stretching, compression, hinging, and bending. These notes help students help in grasping some of the most important concepts, such as stress, strain, Hooke's law and are ideal for brushing up or revision and examinations.
1. Elasticity: Elasticity is a quality that allows an object to restore its original shape after an external force is removed. This implies it shows us how flexible a person's body is. Take, for example, a spring. When a spring is stretched, its shape changes, and when the external force is removed, the spring returns to its original position.
2. Plasticity is the opposite of elasticity. The term "property" refers to a state of permanent deformation. Even when the external force is eliminated, the object never returns to its previous shape. Plastic is the name for these types of items.
3. Ductility: It refers to the ability to be pulled into thin wires or sheets. for example:-Small gold
4. Strength: The ability to resist a high level of applied stress without failing.
Stress = F/A (mathematically)
Where F is the restoring force that emerges in the body as a result of the force we apply.
A=area
It produces a change in volume and density, shape remaining the same.
It occurs in solids, liquids or gases
In the case of fluids, only bulk stress can be found.
It is equal to a change in pressure because the change in pressure is responsible for change in volume.
Volume stress
Strain = ΔL/L, where ΔL is the length change.
L stands for the original length.
Consider a cube with an initial length of L that is in a certain position and is shifted by an angle θ. Let x represent the modest relative displacement.
stress ∝ strain
stress = k × strain
The proportionality constant, k, is also known as the modulus of elasticity.
Here represents p =hydraulic stress, ΔV/V = hydraulic strain
B(solids) > B(liquids) >B(gases)
The letter 'K' stands for this.
k=1/B = - (1/p) (ΔV/V)
k(solids)<k(liquids)<k(gases)
We can also write,
Also, Potential energy per unit volume
Q1: A mild steel wire of length 2L and cross-sectional area A is stretched, well within the elastic limit, horizontally between two pillars. Figure mass m is suspended from the midpoint of the wire. Strain in the wire is:
Answer:
Q2: A rigid bar of mass M is supported symmetrically by three wires, each of length L. Those at each end are of copper, and the middle one is of iron. The ratio of their diameters, if each is to have the same tension, is equal to:
Answer:
As the bar is supported symmetrically by the three wires, therefore extension in each wire is the same.
Let T be the tension in each wire, and the diameter of the wire is D, then Young's modulus is
As F and
Hence,
or
Now, we can find the ratio as
Q3: Consider two cylindrical rods of identical dimensions, one of rubber and the other of steel. Both rods are fixed rigidly at one end of the roof. A mass M is attached to each of the free ends at the centre of the rods. Then:
(a) Both the rods will elongate but there shall be no perceptible change in shape
(b) The steel rod will elongate and change shape but the rubber rod will only elongate
(c) The steel rod will elongate without any perceptible change in shape, but the rubber rod will elongate and the shape of the bottom edge will change to an ellipse
(d) The steel rod will elongate, without any perceptible change in shape, but the rubber rod will elongate with the shape of the bottom edge tapered to a tip at the centre
Answer:
Thus, when mass
Hence, the correct option is (d)
Develops a Good Conceptual Base
Prerequisite to Competitive Exams
Simplifies Complex Topics
Saves Time During Revision
Enhances Problem-Solving
Connects Physics to Real-World Use
Serves as a Consistent Exam Tool
NCERT Class 11 Notes Chapter-Wise are specially crafted to offer efficient study material to help students prepare exams effectively and with ease. These notes are divided into all the chapters of Physics as per the most recent CBSE syllabus with significant formulas, definitions, diagrams, and main ideas. The ability to provide chapter-wise links makes students faster, smarter and stress-free in their revision because the topics needed can be accessed quickly.
Frequently Asked Questions (FAQs)
The elastic modulus is defined as the ratio of tension to strain.
The elastic modulus is a property of each material.
This means that gold will have a specific elastic modulus value, and rubber will have a specific elastic modulus value, and so on.
No, the NCERT notes for Class 11 Physics chapter 8 do not include all of the important derivations. This NCERT note summarizes the chapter's important points and equations and can be used to review the Mechanical Properties of Solids.
From the notes for Class 11 Physics chapter 8, students should expect 4 to 6 mark questions, and they can use this note for quick revision to help them improve their grades.
Volume Strain
The ratio of change in volume to the original volume as a result of hydraulic stress is known as volume strain.
Hooke's law
Within the elastic limit, Hooke's law asserts that the stress developed is directly proportional to the strain produced in a body.
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