Q.Explain the term 'assessment'.

Stress: The Intuition

Imagine holding a heavy book in your palm. Your hand feels a push — a force distributed over the area where the book rests. Now imagine balancing that same book on the tip of your finger. The force is the same (the book's weight), but the area is tiny. The sensation is completely different — it hurts. That difference is stress.

Stress is not just force. It is force spread over an area. The same force concentrated on a small area produces a large stress; spread over a large area, it produces a small stress. This is why a sharp knife cuts easily (small area, large stress) while a blunt knife does not (larger area, smaller stress).

The Precise Definition

Stress ($\sigma$) is defined as the internal restoring force per unit area that develops inside a body when an external deforming force is applied.

Mathematically:

where:

• $F$ is the magnitude of the force applied perpendicular to the cross-section (in newtons, N)
• $A$ is the cross-sectional area over which the force acts (in square metres, m²)
• $\sigma$ is the stress (in pascals, Pa, or N/m²)

Types of Stress

Stress is classified by how the force is applied relative to the surface:

Worked Examples

Example 1: A steel wire of diameter 2 mm supports a load of 100 N. Find the tensile stress.

Area of cross-section: $A = \pi r^2 = \pi (1 \times 10^{-3})^2 = 3.14 \times 10^{-6} \text{ m}^2$ …