Class 8 Science Chapter 6 PDF: Pressure, Winds, Storms, and Cyclones (Curiosity)

Class 8 Science Chapter 6, Pressure, Winds, Storms, and Cyclones, links force and area to pressure in solids, liquids and air, then shows how air-pressure differences drive winds, thunderstorms, lightning and cyclones.

What Class 8 Science Chapter 6 Covers

6.1 Pressure: Megha and Pawan carry identical loads, but Pawan’s bag has thin straps and hurts his shoulders. The same force on a smaller area gives more pressure, which is why a nail is driven point first and a knife cuts with its sharp edge. Pressure is force per unit area, measured in N/m², or pascal (Pa).

Pressure in liquids: in Activity 6.1, balloons tied under pipes of different widths bulge equally when filled to the same height, so liquid pressure depends on the height of the column, not the width of the pipe. Activity 6.2 pokes holes around a bottle to show that water presses sideways too. That is why water tanks sit high up, and why a dam’s base is much broader than its top.

6.2 Pressure exerted by air: the atmosphere of nitrogen, oxygen, argon and carbon dioxide presses on us from every direction. A rubber sucker sticks to a smooth surface because pressing it pushes out most of the air inside, and the air outside then holds it on (Activity 6.4).

6.3–6.4 Wind: uneven heating makes warm air rise and leave low pressure behind, and cooler air from higher-pressure regions rushes in as wind. Blowing between two hanging balloons pulls them together, because high-speed air has lower pressure (Activity 6.6).

6.5 Thunderstorms and lightning: rising warm, moist air builds storm clouds; ice particles rubbing against water droplets build up electric charges, and lightning jumps between clouds or to the ground. Pre-monsoon storms are called Kalboishakhi in West Bengal, Bihar and Jharkhand, Bordoisila in Assam, and mango showers in Kerala, Karnataka and Tamil Nadu. A lightning conductor, a pointed metal rod running from above the roof deep into the ground, carries the charge safely away.

6.6 Cyclones: over a warm ocean, condensing vapour releases heat that pushes the air higher, surrounding air rushes in, and Earth’s rotation sets it spinning. The calm, lowest-pressure centre is the eye, ringed by the strongest winds and rain. Cyclone Amphan in 2020 reached 270 km/h. Once on land a cyclone loses its moisture supply and weakens. The India Meteorological Department (IMD) tracks cyclones and thunderstorms.

Exercises in Chapter 6

• Predict the water level in three connected vessels of different shapes.
• Decide how to get water at higher pressure on the ground floor from a roof tank of height H.
• True or false: air flows from high to low pressure; liquids press only on the bottom; the weather is stormy at the eye of a cyclone; a car is a safe place in a thunderstorm.
• Blow over an 18 cm paper strip, predict what happens and explain it; list three major cyclones that hit India.

Read Class 8 Science Chapter 6 Online

More Chapters

• Previous: Chapter 5: Exploring Forces
• Next: Chapter 7: Particulate Nature of Matter
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FAQ

Why are water tanks placed at a height?
Because liquid pressure increases with the height of the water column, so a higher tank gives more pressure at the taps below.

What is the eye of a cyclone?
The calm centre of a cyclone, where air pressure is lowest; the strongest winds and heaviest rain surround it.

What are mango showers?
Pre-monsoon thunderstorms in Kerala, Karnataka and Tamil Nadu that help mangoes ripen; the same storms are called Kalboishakhi in West Bengal and Bordoisila in Assam.

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