🌪️ Class 8 Science
Chapter 6: Pressure, Winds, Storms, and Cyclones
Based on NCERT "Curiosity" (2024). Simple notes for easy learning. Not a textbook replacement.
🌐 Real-World Connection: Have you ever noticed that the thin heels of high-heeled shoes sink into soft ground, while flat shoes spread your weight over a larger area and don't sink? Same person, same weight — but very different pressure! Understanding pressure explains snowshoes, sharp knives, blunt knives, why deep water crushes things, how weather patterns form, and why cyclones are so destructive. Pressure is one of the most powerful and invisible forces around us every day.
💪 Topic 1: What is Pressure
Pressure is force on a small area.
More force on less area means more pressure.
A nail has a sharp tip, so it pushes in.
A flat shoe gives less pressure on ground.
Pressure = Force ÷ Area (simple formula).
💧 Topic 2: Pressure in Liquids
Water pushes on things inside it.
Deeper water has more pressure.
A dam is thick at the bottom for this.
Water pushes in all directions equally.
Divers feel more pressure when they go deep.
🌍 Topic 3: Atmospheric Pressure
Air around us has weight and pushes us.
This pushing by air is atmospheric pressure.
We do not feel it because we are used to it.
On mountains, air pressure is less.
At sea level, air pressure is more.
🌬️ Topic 4: Air Pressure and Wind
Wind is moving air from place to place.
Air moves from high pressure to low pressure.
Warm air goes up because it is light.
Cool air comes down to fill the space.
This movement of air makes wind blow.
⬆️ Topic 5: High and Low Pressure Areas
High pressure area has cool, heavy air.
Low pressure area has warm, light air.
Air always moves from high to low pressure.
Low pressure areas often have clouds and rain.
High pressure areas usually have clear sky.
🍃 Topic 6: How Wind is Formed
The sun heats land and water differently.
Hot land heats the air above it quickly.
This hot air rises up into the sky.
Cool air from the sea rushes in to fill.
This is how sea breeze works near coasts.
⛈️ Topic 7: Thunderstorms and Cyclones
A thunderstorm has rain, lightning, and wind.
It happens when hot air rises very fast.
A cyclone is a very big, spinning storm.
Cyclones form over warm ocean water.
They bring heavy rain and strong winds.
👁️ Topic 8: Structure of a Cyclone
The center of a cyclone is the eye.
The eye is calm with no wind or rain.
Around the eye is the eye wall.
The eye wall has the strongest winds.
Outside the eye wall, wind gets weaker.
🛡️ Topic 9: Safety During Cyclones
Stay inside a strong building during a cyclone.
Keep away from windows and glass doors.
Listen to radio or TV for safety news.
Store water, food, and a torch at home.
Move to higher ground if flooding starts.
🌡️ Topic 10: Weather Instruments — Barometer
A barometer measures air pressure.
Falling pressure means a storm may come.
Rising pressure means clear weather ahead.
A wind vane shows the direction of wind.
An anemometer measures how fast wind blows.
🎨 Section 2 — Visual Diagrams
Diagram 1: Big Area vs Small Area — How Pressure Changes
Diagram 2: Water Pressure Increases with Depth
Diagram 3: Sea Breeze — How Wind Forms Near the Coast
Diagram 4: Inside a Cyclone — Eye, Eye Wall, and Rain Bands
Diagram 5: Five Weather Instruments Scientists Use
🧩 Section 3 — Solved Examples
💪 Example 1: Calculating Pressure
A box pushes with 20 N force. Its base is 4 square metres. What is the pressure?
1
Write the formula: Pressure = Force ÷ Area.
2
Force = 20 N. Area = 4 m².
3
Pressure = 20 ÷ 4 = 5.
4
The unit is N/m² or Pascal (Pa).
Answer: The pressure is 5 Pa (Pascals).
🌬️ Example 2: Which Way Does Wind Blow?
City A has high air pressure. City B has low air pressure. Which way does the wind blow?
1
Wind moves from high to low pressure.
2
City A has high pressure.
3
City B has low pressure.
4
So wind blows from A to B.
Answer: Wind blows from City A to City B.
👁️ Example 3: Parts of a Cyclone
Ravi says the eye of a cyclone has the strongest wind. Is he right or wrong?
1
The eye is the center of a cyclone.
2
The eye is calm with no wind.
3
The eye wall has the strongest winds.
4
So Ravi is wrong about the eye.
Answer: Ravi is wrong. The eye is calm. The eye wall has the strongest wind.
📖 Section 4 — Key Terms Table
Word
What It Means (Simple)
Example
Pressure
Force pushing on an area
Nail pushes into wall easily
Atmosphere
Blanket of air around Earth
We breathe air from it
Atmospheric Pressure
Weight of air pushing down
Air presses on our body
Wind
Moving air from one place to another
Breeze on a hot day
High Pressure
Cool heavy air pushing down hard
Clear sunny weather
Low Pressure
Warm light air rising up
Cloudy or rainy weather
Sea Breeze
Wind blowing from sea to land
Cool air near beach in daytime
Thunderstorm
Storm with thunder, lightning, rain
Big storm on a hot day
Cyclone
Huge spinning storm over ocean
Cyclone Fani hit India in 2019
Eye
Calm center of a cyclone
No wind or rain in the eye
Eye Wall
Ring around the eye, strongest wind
Most dangerous part of cyclone
Barometer
Tool that measures air pressure
Falling reading means storm coming
✏️ Section 5 — Practice Worksheets
Part A: Fill in the Blanks
1. Pressure equals force divided by __________.
2. Air moves from high pressure to __________ pressure.
3. The calm center of a cyclone is the __________.
4. A __________ measures air pressure.
5. Deeper water has __________ pressure.
Part B: True or False
1. A nail goes in easily because of high pressure. ( )
2. The eye of a cyclone has the strongest wind. ( )
3. Wind blows from low pressure to high pressure. ( )
4. Warm air is lighter than cool air. ( )
5. A barometer measures wind speed. ( )
Part C: Short Answer
1. Why does a sharp knife cut better than a dull one?
2. What happens when warm air rises?
3. Name two things you should do during a cyclone.
Part D: Match the Columns
Column A
1. Barometer
2. Wind vane
3. Anemometer
4. Rain gauge
5. Thermometer
Column B
a. Wind speed
b. Temperature
c. Air pressure
d. Rainfall
e. Wind direction
Part E: Draw and Label
Draw a cyclone. Label the eye, eye wall, and rain bands.
✅ Detailed Solutions — Section 5
Part A: Fill in the Blanks
Pressure equals force divided by area.
Air moves from high pressure to low pressure.
The calm centre of a cyclone is the eye.
A barometer measures air pressure.
Deeper water has more (higher) pressure.
Part B: True or False
True — A nail's sharp tip concentrates the same force onto a very tiny area, creating very high pressure, so it goes in easily.
False — The eye of a cyclone is the calmest part with no wind. The eye wall has the strongest winds.
False — Wind blows from high pressure to low pressure, not the other way.
True — Warm air is less dense (lighter) than cool air, so it rises, creating a low pressure area below.
False — A barometer measures air pressure. An anemometer measures wind speed.
Part C: Short Answer
A sharp knife has a very thin, small area along its edge. When you apply the same cutting force, that force is concentrated on a tiny area, creating very high pressure. A dull knife has a wider edge — the same force spread over more area gives less pressure, so it cannot cut as well.
When warm air rises, the air pressure at the surface drops (becomes low). Cooler, heavier air from surrounding areas rushes in to fill the low pressure zone. This movement of air is wind. If the temperature difference is large, very strong winds form, leading to storms.
Two safety actions during a cyclone: (a) Move to a strong concrete building and stay indoors away from windows. (b) Stay away from trees, electric poles, and the coast — listen to weather alerts and follow official instructions.
Part D: Match the Columns
Barometer → c. Air pressure
Wind vane → e. Wind direction
Anemometer → a. Wind speed
Rain gauge → d. Rainfall
Thermometer → b. Temperature
Part E: Draw and Label
Draw three concentric circles (rings inside rings):
Innermost circle: label it "Eye" — calm, no wind, clear sky
Next ring: label it "Eye Wall" — strongest winds and heaviest rain, most dangerous zone
Outer ring: label it "Rain Bands" — spiral bands of clouds and rain spiralling inward
Draw curved arrows around the whole diagram showing the anti-clockwise spiral (in the Northern Hemisphere)
🔄 Section 6 — Flip & Learn Cards
Click each card to see the answer!
What is pressure?
Force pushing on an area. Pressure = Force ÷ Area.
Why does a nail go in easily?
It has a tiny sharp tip. Same force on small area = high pressure.
What is atmospheric pressure?
The weight of air around us pushing on everything.
How does wind form?
Air moves from high pressure to low pressure areas.
What is a cyclone?
A huge spinning storm that forms over warm ocean water.
What is the eye of a cyclone?
The calm center with no wind or rain.
What is the eye wall?
The ring around the eye with the strongest winds.
What does a barometer do?
It measures air pressure. Falling pressure means a storm.
🧠 Section 7 — Mind Map
Mind Map: All Topics at a Glance — Pressure, Winds, Storms, and Cyclones