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Pressure, Winds, Storms, and Cyclones - Pressure

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Pressure is defined as the force acting per unit area on a surface: P=ForceAreaP = \frac{Force}{Area}.

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The SI unit of pressure is the Pascal (PaPa), which is equivalent to 1 Newton per square metre (N/m2)1\text{ Newton per square metre (N/m}^2).

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For a constant force, pressure is inversely proportional to the area (P∝1AP \propto \frac{1}{A}). A smaller area results in higher pressure, while a larger area results in lower pressure.

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Air around us exerts pressure in all directions, known as atmospheric pressure.

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Heating causes air to expand. Expanded air occupies more volume, becomes less dense (lighter), and rises, creating a region of low pressure.

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Wind is the movement of air caused by pressure differences; air always moves from a region of high pressure to a region of low pressure.

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High-speed winds are accompanied by reduced air pressure. This is why roofs can be lifted during a high-speed storm as the pressure above the roof drops significantly compared to the pressure inside the house.

📐Formulae

P=FAP = \frac{F}{A}

Pressure=ForceArea\text{Pressure} = \frac{\text{Force}}{\text{Area}}

1 Pa=1 N/m21\text{ Pa} = 1\text{ N/m}^2

💡Examples

Problem 1:

A force of 150 N150\text{ N} is applied over an area of 0.03 m20.03\text{ m}^2. Calculate the pressure exerted.

Solution:

Given: F=150 NF = 150\text{ N} and A=0.03 m2A = 0.03\text{ m}^2. Using the formula P=FAP = \frac{F}{A}, we have: P=1500.03=5000 PaP = \frac{150}{0.03} = 5000\text{ Pa}.

Explanation:

By dividing the total force by the area of contact, we determine that the pressure is 5000 Pascals5000\text{ Pascals}.

Problem 2:

If the atmospheric pressure at point A is 101300 Pa101300\text{ Pa} and at point B it is 98500 Pa98500\text{ Pa}, calculate the pressure difference.

Solution:

101300−985002800\begin{array}{r} 101300 \\ - 98500 \\ \hline 2800 \end{array} The pressure difference is 2800 Pa2800\text{ Pa}.

Explanation:

The pressure difference is found by subtracting the lower pressure value from the higher pressure value using vertical subtraction.

Problem 3:

Why is it easier to cut an apple with the sharp edge of a knife than with the blunt edge?

Solution:

The sharp edge has a very small area (AA). Since P=FAP = \frac{F}{A}, a small area produces a very high pressure for the same amount of force (FF).

Explanation:

High pressure allows the knife to pierce the surface of the apple easily, whereas the blunt edge has a larger area and produces less pressure.