**Mechanical Properties of Solids-**

Before you go through this article, make sure that you have gone through the previous article on **Introduction to Elasticity**.

**We have learnt-**

- Under the action of
**deforming force**, the**original configuration**of the body**changes**. - The
**molecules**of the body suffers a**relative displacement**which gives rise to a restoring force. - The
**restoring force**developed inside the body tries to**restore its original configuration**.

**In this article, we will learn about stress and its types.**

**Stress-**

In mechanical properties of solids, stress is defined as-

The restoring force per unit area of the body is called as stress. |

The restoring force is equal and opposite to the deforming force. Therefore,

Stress may also be defined as the deforming force per unit area of the body. |

**Mathematically,**

**Characteristics of Stress-**

- The SI unit of stress is
**newton per square meter (N/m**.^{2}) - The unit of stress is also a
**pascal (Pa)**. 1 Pa = 1 Nm^{-2} - The dimensional formula of stress is same as that of pressure i.e.
**[ML**^{-1}T^{-2}] - Stress is a
**scalar quantity**. - The
**effect of stress**is to produce distortion i.e. change the original configuration of the body.

**Types of Stress-**

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

**1. Normal Stress or Longitudinal Stress-**

It is of two types-

- Tensile Stress
- Compressive Stress

**Tensile Stress-**

- When two equal and opposite forces are applied at the ends of a solid rod to increase its length, then the body is under tensile stress.
- Under tensile stress, a restoring force equal to the applied force normal to the cross-sectional area of the rod comes into existence.
- This restoring force acting per unit area perpendicular to the cross-section of the body is called as
**tensile stress**.

**Compressive Stress-**

- When two equal and opposite forces are applied at the ends of a solid rod to decrease its length or to compress it, then the body is under compressive stress.
- Under compressive stress, a restoring force equal to the applied force normal to the cross-sectional area of the rod comes into existence.
- This restoring force acting per unit area perpendicular to the cross-section of the body is called as
**compressive stress**.

**2. Tangential Stress or Shearing Stress-**

- When two equal and opposite forces act along the tangents to the surfaces of the opposite faces of an object, then the object is under shearing stress.
- Under shearing stress, one face of the object is displaced with respect to the other face.
- The ratio of the force acting along the tangent to the surface to the area of the surface is called as
**shearing stress**.

**3. Bulk Stress or Volume Stress or Hydraulic Stress-**

- When an object is immersed in a fluid (liquid or gas), the fluid exerts force on the surfaces of the object, then the object is under bulk stress.
- Under bulk stress, the volume of the object decreases.
- The ratio of the force acting perpendicular to the surface of the object per unit area of the object is called as
**bulk stress**.

**Read the next article on-**

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