**Stress & Strain | Mechanical Properties of Solids-**

Before you go through this article, make sure that you have gone through the previous articles on **Stress** and **Strain**.

**We have learnt-**

- When a
**deforming force**is applied on a body, a restoring force is produced in it. - This
**restoring force**per unit area of the body is called as**stress**. - The
**effect of stress**is to produce**distortion**or change the configuration of the body. - The ratio of the change in configuration to the original configuration is called as
**strain**. - Strain measures the
**degree of deformation**.

**In this article, we will learn about Hooke’s Law and Modulus of Elasticity.**

**Hooke’s Law-**

In mechanical properties of solids, Hooke’s law is defined as-

For sufficiently small stresses, stress is directly proportional to the strain. |

**Mathematically,**

Here, this constant is called **Modulus of Elasticity** or **Elastic Modulus**. Thus,

**Characteristics of Modulus of Elasticity-**

- Its SI unit is same as that of stress i.e.
**newton per square meter (Nm**or^{-2})**pascal (Pa)**. - Its dimensional formula is same as that of stress i.e.
**[ML**.^{-1}T^{-2}] - It is a
**scalar quantity**. - Its value depends on the
**nature of material**of the body and is independent of its dimensions. - It is a measure of
**rigidity or stiffness**of a material. Greater the modulus, the stiffer the material.

**Types of Modulus of Elasticity-**

Since strain is of three types, therefore modulus of elasticity is also of three types-

**Let us discuss all types of modulus of elasticity one by one in detail.**

**1. Young’s Modulus of Elasticity-**

It is defined as the ratio of the longitudinal stress on the material to the longitudinal strain produced in the material.

**2. Bulk Modulus of Elasticity-**

It is defined as the ratio of the bulk stress (or volume stress) on the material to the volume strain produced in the material.

**3. Shear Modulus or Modulus of Rigidity-**

It is defined as the ratio of the tangential stress (or shearing stress) on the material to the shear strain produced in the material.

**Read the next article on-**

**Elastic Potential Energy In Stretched Wire**

**Get more notes & other study material of the Chapter** **Mechanical Properties of Solids**.