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Notes : Elastic Potential Energy Stored in a Stretched Wire: Derivation, Formula, Energy Density, Numericals, MCQs , FAQs Class 11 physics chapter 8 mechanical - Physicskund  Introduction When an external force stretches a wire, work is done against the internal restoring forces of the material. This work gets stored in the wire as Elastic Potential Energy (EPE) . If the wire is within its elastic limit, the stored energy can be completely recovered when the force is removed. Basic Terms Stress Stress is defined as the restoring force acting per unit area. $$ \text{Stress}=\frac{F}{A} $$ Where: \(F\) = Applied Force \(A\) = Area of Cross-section SI Unit: Pascal (Pa) Strain Strain is the ratio of change in length to the original length. $$ \text{Strain}=\frac{\Delta L}{L} $$ or $$ \text{Strain}=\frac{l}{L} $$ Where: \(l\) = Extension Produced \(L\) = Original Length SI Unit: No Unit (Dimensionless) Young's Modulus Young's m...

Poisson’s Ratio: Definition, Formula, Derivation, Properties, Numericals, MCQs, FAQs - Physicskund 1. Introduction When a force is applied to a material, its dimensions change. For example, when a wire is stretched: Its length increases. Its diameter decreases. The strain produced along the direction of the applied force is called longitudinal strain , while the strain produced perpendicular to the applied force is called lateral strain . French mathematician and physicist Siméon Denis Poisson observed that within the elastic limit, lateral strain is proportional to longitudinal strain. This observation led to the concept of Poisson’s Ratio . 2. Lateral Strain The strain produced perpendicular to the direction of the applied force is called lateral strain . Formula If: Original diameter of wire = \(d\) Change (decrease) in diameter = \(\Delta d\) \[ \text{Lateral Strain} = \frac{\Delta d}{d} \] 3. Longitudinal Strain The strain produced in the dir...

Hooke's Law and Stress-Strain Curve Notes | Class 11 Physics Chapter 8 | IIT JEE, NEET & NCERT - Physics kund When a force is applied to a body, it undergoes deformation. The relationship between stress and strain is explained by Hooke's Law, while the complete behaviour of a material under load is represented by the Stress–Strain Curve. Hooke's Law Definition: Hooke's Law states that within the elastic limit, stress is directly proportional to strain. Mathematical Expression: $\text{Stress} \propto \text{Strain}$ $\text{Stress} = k \times \text{Strain}$ where: Stress = Restoring force per unit area Strain = Fractional change in dimension $k$ = Modulus of Elasticity (proportionality constant) Important Points of Hooke's Law • Valid only for small deformations. • Applicable only within the elastic limit. • It is an empirical law based on experiments. • Most solids obey Hooke's law up to a certain limit. • Rubber and biological tis...

Stress and Strain are important concepts used to explain the deformation of solids when external forces act on them. When a body is subjected to a deforming force, its length, shape, or volume may change. The study of stress and strain helps us understand the elastic behaviour of materials. What is Stress? When an external deforming force acts on a body, internal restoring forces develop within the body to oppose the deformation. The restoring force acting per unit area is called Stress . Definition of Stress Stress is defined as the restoring force acting per unit area inside a body when an external deforming force acts on it. Symbol of Stress $ \sigma $ Formula of Stress $ \sigma = \frac{F}{A} $ Where: $ F $ = Restoring Force $ A $ = Area of Cross-section SI Unit of Stress Pascal (Pa) or N m -2 Dimensional Formula of Stress $ [ML^{-1}T^{-2}] $ Types of Stress 1. Longitudinal Stress When the deforming force acts perpendicular (normal) to...

Learn the concepts of Elastic, Elasticity, Plasticity, Perfectly Elastic Body, and Perfect Plastic Body in Class 11 Physics Chapter 8. Includes definitions, examples, FAQs, MCQs, true-false questions, and short answer questions for NCERT, JEE, and NEET preparation in Physicshund 1. Elastic A material is said to be elastic if it regains its original shape and size after the removal of the deforming force. Example: Steel spring, quartz fibre. 2. Elasticity Elasticity is the property of a material by virtue of which it regains its original shape and size completely when the deforming force is removed. Ncert Definition  Elasticity is the property of a body that enables it to regain its original configuration after the removal of the deforming force. 3. Perfectly Elastic Body A body that completely regains its original shape and size after the removal of the deforming force is called a perfectly elastic body . Example: No material is perfectly elastic in practice, b...