இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

**Properties of solids**

**Elasticity:**

A body regains its original shape and size after the removal of deforming force, it is said

to be elastic and the property is called elasticity. The force which changes the size or

shape of a body is called a deforming force.

Examples: Rubber, metals and steel ropes.

**Plasticity:**

If a body does not regain its original shape and size after removal of the deforming force,

it is said to be a plastic body and the property is called plasticity.

Example: Glass

**Elastic limit:**

Boundary act as the linkage between elasticity and plasticity is called as Elastic limit.

Properties of Solids:

**Stress:**

The force per unit area is called as stress.

Stress = force/area.

The SI unit of stress is Nm -2 or pascal (Pa)

Its dimension is [ML -1 T -2 ]. Stress is a tensor

**Types:**

Longitudinal stress

o Tensile stress

**o Compressive stress**

Shear or tangential stress

Volumetric stress (pressure)

**Longitudinal stress:**

Stress either by stretching or compression is called longitudinal stress.

**Tensile stress:**

Internal forces on the two sides of a body may pull each other, i.e., it is stretched by equal and

opposite forces. Then, the longitudinal stress is called tensile stress.

**Compressive stress:**

When forces acting on the two sides of a body push each other, then body is pushed by equal and

opposite forces at the two ends. It is said to be under compression. Then, the longitudinal stress

is called compressive stress.

**Shear Stress:**

Stress due to shearing of a material is called as Shear Stress.

**Volumetric stress:**

It happens when a body is acted by forces everywhere on the surface. The value of the

volumetric stress is equal to Pressure in fluids.

**Strain:**

It is the ratio of change in dimension by original dimension. Itis a dimensionless quantity and has

no unit.

**Longitudinal strain:**

It is the ratio of increase or decrease in the length of the material to the actual or natural size of

the material.

**Tensile strain:**

If the length is increased from its natural length then it is known as tensile strain.

**Compressive strain:**

If the length is decreased from its natural length then it is known as compressive strain.

**Shearing strain:**

(Angle of shear)

Where x gives the value of shear strain

**Volumetric strain:**

It is the ratio of Change in volume by original volume.

Moduli of elasticity:

It’s the ratio of stress by strain

**Young’s modulus:**

When a wire is stretched or compressed, then the ratio between tensile stress (or

compressive stress) and tensile strain (or compressive strain) is defined as Young’s

modulus.

The unit for Young modulus has the same unit of stress because, strain has no unit. So,

S.I. unit of Young modulus is Nm -2 or pascal.

**The rigidity modulus or shear modulus:**

The rigidity modulus is defined as Rigidity modulus or Shear modulus ratio of Shearing stress by

shearing strain

**Bulk modulus:**

Bulk modulus is defined as the ratio of volume stress to the volume strain.

**Relationship between modulus of elasticity:**

E = 9KG / (G + 3K)

E = young modulus

G = modulus of rigidity or shear modulus

K = Bulk modulus

**Poisson’s ratio:**

It is defined as the ratio of relative contraction (lateral strain) to relative expansion (longitudinal

strain). It is denoted by the symbol μ.

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