 # Elasticity – Elastic And Inelastic Materials

This article gives you a summary of Elasticity and types of materials, you will also learn the Hooke’s Law, read more on stress and strain and its formula likewise the Young Modulus, longitudinal stress and strain and finally, the modulus of elasticity.

## ELASTICITY

Elasticity, This is the ability of a material to regain its original shape and size after been distorted by an external force.

### Elastic Material

It is/they are materials that return to its original shape and size after distorting force has been removed or after deformation. ### Inelastic Material

It is/they are materials that do not return to its original shape and size after deformation.

HOOKE’S LAW

It states that provided that the elastic unit of an elastic material is not exceeded the extension “e” of the material is directly proportional to the load or applied force “f”.

Formula: F= -KE

To find the spring constant; K = F ÷ Change in length.

### STRESS

It is the ratio of applied force “F” to the area “A” over which it acts.

Stress = Force ÷ Area

Unit for stress is “Pa”

### STRAIN

It is the relative change in dimension or shape of a body as the result of applied stress.

Strain = change in length ÷ original length.

### LONGITUDINAL STRESS AND STRAIN

For wire, rod, and bar there is longitudinal stress that produces a change in length per unit length. ### ELASTIC LIMIT

It is the maximum stress a body can experience without being permanently deformed

NB: If the stress exceeds the ultimate strength, the material break.

### MODULUS OF ELASTICITY

Provided that the elastic limit is not exceeded and elastic deformation (strain) is directly proportional to the magnitude of the applied force per unit area.

Formula = stress ÷ strain.

### YOUNG MODULUS

For materials whose length is much greater than the width or thickness, we are concerned with the longitudinal modulus of elasticity.

Y= stress ÷ strain = F/A ÷ change in length divided by the original length.