krit.club logo

Pressure, Winds, Storms, and Cyclones - Cyclone

Grade 8CBSE

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

🔑Concepts

•

Air exerts pressure on all objects around us. High-speed winds are always accompanied by reduced air pressure in that region.

•

Air moves from the region where the air pressure is high to the region where the pressure is low. The greater the difference in pressure, the faster the air moves.

•

On heating, air expands and occupies more space. Since it occupies more volume for the same mass, warm air becomes lighter than cold air and rises up.

•

A thunderstorm develops in hot, humid tropical areas. The rising temperatures produce strong upward rising winds which carry water droplets upwards, where they freeze and fall down again.

•

A cyclone is a large-scale air mass that rotates around a strong center of low atmospheric pressure. Factors like wind speed, wind direction, temperature, and humidity contribute to the development of cyclones.

•

The center of a cyclone is a calm area called the 'eye' of the storm. Its diameter varies from 1010 to 3030 km. It is a region free of clouds and has light winds.

•

Around the eye is a region of about 150150 km in size, where there are high-speed winds (up to 150−250150-250 km/h) and thick clouds with heavy rain.

•

Cyclones are known by different names in different parts of the world: 'Hurricane' in the American continent and 'Typhoon' in Japan and Philippines.

📐Formulae

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

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

Wind Speed∝1Air Pressure\text{Wind Speed} \propto \frac{1}{\text{Air Pressure}}

💡Examples

Problem 1:

A force of 400400 N is applied over an area of 22 m2m^2. Calculate the pressure exerted. If the same force is applied over a smaller area of 0.50.5 m2m^2, how does the pressure change?

Solution:

Case 1: P1=4002=200P_1 = \frac{400}{2} = 200 N/m2N/m^2. Case 2: P2=4000.5=800P_2 = \frac{400}{0.5} = 800 N/m2N/m^2.

Explanation:

In the first case, the pressure is 200200 Pa. In the second case, because the area decreased by a factor of 44, the pressure increased by a factor of 44 to 800800 Pa. This illustrates that for the same force, a smaller area results in higher pressure.

Problem 2:

Explain why a bicycle tube bursts if it is overfilled with air, especially during hot summers.

Solution:

When air is pumped into the tube, the number of air molecules increases, increasing the internal pressure. During summer, the heat causes the air inside the tube to expand (V∝TV \propto T).

Explanation:

The expansion of air increases the pressure exerted on the walls of the tube. If the pressure exceeds the strength of the rubber, the tube bursts. This demonstrates that air expands on heating.

Problem 3:

Calculate the difference in pressure exerted by two winds if the first wind exerts a force of 15001500 N over 1010 m2m^2 and the second exerts 25002500 N over 2020 m2m^2.

Solution:

Area 1 Pressure: P1=150010=150 PaP_1 = \frac{1500}{10} = 150 \text{ Pa} Area 2 Pressure: P2=250020=125 PaP_2 = \frac{2500}{20} = 125 \text{ Pa} Difference: 150−12525\begin{array}{r} 150 \\ - 125 \\ \hline 25 \end{array}

Explanation:

The first wind exerts a pressure of 150150 Pa and the second exerts 125125 Pa. The pressure difference is 2525 Pa. Air would naturally tend to move from the region of 150150 Pa towards the region of 125125 Pa.