Class 11th Physics Ch-9 Mechanical Properties of Solids Study Notes

BASIC CONCEPTS (INTRODUCTION)

ELASTICITY AND PLASTICITY

ELASTIC BEHAVIOUR OF SOLIDS

STRESS AND STRAIN

Stress

Types of Stress

Strain

SOLVED EXAMPLES

Illustration-01

Solution

Illustration-02

Solution

HOOKE’S LAW

Hooke’s Law

STRESS-STRAIN CURVE

Stress-Strain Curve

Elastic Limit

Elastic Hysteresis

Elastomers

Substances like tissue of aorta, rubber etc. which can be stretched to cause large strains are called elastomers.

ELASTIC MODULUS

Elastic Modulus

The modulus of elasticity or coefficient of elasticity of a body is defined as the ratio of the stress to the corresponding strain produced.

Elastic Modulus

Relation between Y, B, η and σ

ELASTIC POTENTIAL ENERGY

Elastic Potential Energy

POISSON’S RATIO

Poisson’s Ratio

            Value of σ lies between 0 and 0.5

APPLICATIONS OF ELASTIC BEHAVIOUR OF MATERIALS

Applications

(1) The bridges are designed in such a way that they do not bend much or break under the load of heavy traffic, force of strongly blowing wind and its own weight. So the beams used in constructions of bridges, as supports are made in shape of I.
(2) The metallic parts of the machinery are never subjected to a stress beyond elastic limit, otherwise they will get permanently deformed.
(3) The thickness of the metallic rope used in the crane in order to lift a given load is decided from the knowledge of elastic limit of the material of the rope and the factor of safety.