Mechanical Properties of Solids Class 11th Notes PDF

# UDAY 2025 ## FOR CLASS 11TH ### Chapter 11 - PHYSICS ### Lecture 02 - Mechanical Properties of Solids #### By - ER. RAKSHAK SIR # Topics to be covered 1. Stress-Strain Curve 2. ... 3. ... # Stress vs Strain Curve (For Ductile Materials) - Stress and Strain of a material are represented on an x-y...

# UDAY 2025 ## FOR CLASS 11TH ### Chapter 11 - PHYSICS ### Lecture 02 - Mechanical Properties of Solids #### By - ER. RAKSHAK SIR # Topics to be covered 1. Stress-Strain Curve 2. ... 3. ... # Stress vs Strain Curve (For Ductile Materials) - Stress and Strain of a material are represented on an x-y graph, called the Stress-Strain Curve. - The entire graph for a ductile material is divided into five different ranges: | Range | Description | |---|---| | OA | Elastic Range - Stress is proportional to strain | | AB | Elastic Range | | BC | For very less stress, there is a significant strain | | CD | Unsafe to use- Necks are seen | # Curve for Brittle Materials and Elastomers - Brittle materials have a stress-strain graph with a steep slope, which means that they break at low strains. - Examples: Cast Iron, Glass - Elastomers have a stress-strain curve with a very shallow slope, which means that they have a high strain at fracture. - Examples: Rubber, Aorta # Effect of Temperature on Young's Modulus - When temperature increases, Young's Modulus decreases. This is because the inter-particle forces decrease with increasing temperature. # Elongation in a Wire - The elongation of a wire is proportional to the applied force, the length of the wire, and the cross-sectional area of the wire. - The formula for elongation is: $ΔL = \frac{FL}{YA}$ where: * ΔL is the elongation of the wire * F is the applied force * L is the length of the wire * Y is Young's Modulus of the wire * A is the cross-sectional area of the wire # Elongation in a Wire with Mass Attached - The elongation of a wire with a mass attached is proportional to the weight of the mass, the length of the wire, and the cross-sectional area of the wire. - The formula for elongation is: $ΔL = \frac{MgL}{YA}$ where: * ΔL is the elongation of the wire * M is the mass * g is acceleration due to gravity * L is the length of the wire * Y is Young's Modulus of the wire * A is the cross-sectional area of the wire # Graph - The slope of the stress-strain curve is Young's Modulus. - Within the elastic limit (Proportional Limit), the stress is proportional to the strain. This is known as Hooke's Law. # Relation with spring - The spring constant, k, is proportional to the Young's Modulus of the wire and the cross-sectional area of the wire, and inversely proportional to the length of the wire. - The formula for spring constant is:  $K = \frac{YA}{L}$ # Elastic Potential Energy - The elastic potential energy of a stretched wire is proportional to the square of the elongation. - The formula for elastic potential energy is: $U= \frac{1}{2} (Stress)(Strain)(Volume)$ # Breaking Stress - Breaking Stress is the stress at which a material breaks. - Breaking stress is proportional to the force applied and inversely proportional to the area of the object. # Poisson's Ratio - Poisson's ratio is the ratio of lateral strain to longitudinal strain. - The formula for Poisson's ratio is: $σ= \frac{-ΔR/R}{ΔL/L}$ # Homework - 2-3 pages of routine practice including formulas and one line concepts. # Thank You