Elasticity - Physics Class 11

Stress

The force per unit area acting on an object. It quantifies the intensity of internal forces in materials and is measured in Pascals (Pa).

Strain

The relative deformation or change in a shape or size of an object due to applied stress. It is a dimensionless quantity.

Types of strain

Tensile stress, shear strain, and volumetric strain.

Hooke’s law

States that for small deformations, the stress in a material is directly proportional to the strain.

Elastic Moduli

Young’s modulus, shear modulus, and bulk modulus.

Young’s Modulus

It relates tensile stress to tensile strain. It is a measure of stiffness in response to stretching or compressing.

Shear Modulus

It relates shear stress to shear strain. It is a measure of resistance to twisting or cutting forces.

Bulk’s Modulus

It relates volumetric stress to volumetric strain. It is a measure of a material’s reistance to compression under uniform pressure.

Elastic limit

The maximum stress that a material can withstand without undergoing permanent deformation. Beyond this point, the material will not return to its original shape.

Yield strength

The maximum stress a material can withstand while still being able to return to its original shape after the removal of the load. It marks the transition from elastic to plastic deformation.

Ultimate Tensile Strength (UTS)

The maximum stress that a material can endure while being stretched or pulled before failing or breaking. It represents the peak stress in the material's stress-strain curve.

Ductile materials

Substances that can undergo significant plastic deformation before rupture (such as copper and steel). They exhibit high tensile strength and can be drawn into wires, allowing for extensive stretching under stress.

Brittle materials

Substances that fracture without significant plastic deformation when subjected to stress. They tend to break easily under tension, with little to no elongation, such as glass and ceramics.