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Overview

What is Pressure?

January 15, 2025
1 min read
pressure force area

The Concept of Pressure

Imagine two students, Megha and Pawan, carrying identical heavy bags. Megha is comfortable, but Pawan is in pain.

  • Megha’s Bag: Broad straps.
  • Pawan’s Bag: Narrow straps.

Why does the narrow strap hurt more? The weight (force) is the same, but the area of contact is different.

Definition

Pressure is the force acting perpendicularly on a unit area of a surface.

Pressure=ForceArea\text{Pressure} = \frac{\text{Force}}{\text{Area}}
  • SI Unit: Newton per square metre (N/m2N/m^2), also called Pascal (Pa).

Effect of Area on Pressure

Since Area is in the denominator of the formula, changing the area has the opposite effect on pressure.

  1. Decreasing Area increases Pressure:

    • Knives: Have very sharp edges (small area) to cut easily with less force.
    • Nails: Have pointed tips to drive into walls easily.

  2. Increasing Area decreases Pressure:

    • School Bags: Wide straps spread the weight over a larger shoulder area, reducing pain.
    • Porters: Place a round cloth (pagdi) on their heads to increase the contact area for heavy loads.
    • Dams: Have broad bases to withstand high water pressure at the bottom.

Visualizing Pressure

Force (100N)Small Area = High PressureForce (100N)Large Area = Low Pressure
Note

Example Calculation: If a force of 100 N100 \text{ N} acts on an area of 2 m22 \text{ m}^2: P=1002=50 PaP = \frac{100}{2} = 50 \text{ Pa} If the same force acts on an area of 1 m21 \text{ m}^2: P=1001=100 PaP = \frac{100}{1} = 100 \text{ Pa} Halving the area doubles the pressure!