Class 8 Science Chapter 6 – Pressure, Winds, Storms, and Cyclones from NCERT Curiosity with easy Notes and complete Book Solutions. Get simple explanations, important concepts, questions and answers, and revision material for effective learning, practice and exam preparation.

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Pressure, Winds, Storms, and Cyclones

Class 8 Science – Curiosity

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Chapter in simple words: This chapter explains pressure, pressure exerted by liquids and air, formation of winds, storms, thunderstorms, lightning and cyclones.

1. Probe and Ponder

Why are winds stronger on some days than on others?

Winds become stronger when the difference in air pressure is greater.

Why are water tanks usually placed at a height?

A higher water tank produces greater water pressure and gives a stronger flow of water.

Can air pressure really crush us?

Atmospheric pressure is very large, but the pressure inside our body balances the pressure outside.

What causes storms and cyclones? If the Earth stopped rotating, would cyclones still form?

Storms form due to rising warm moist air, pressure differences and strong winds. Cyclones form over warm ocean water and Earth’s rotation makes the moving air spin.

Share your questions

Write your own questions about pressure, winds, storms and cyclones.

2. Easy Notes and Concepts

Pressure: Pressure is the force acting per unit area.

Pressure = Force ÷ Area

SI unit of pressure: N/m², also called pascal (Pa).

Effect of area: Smaller area produces greater pressure for the same force. Larger area produces smaller pressure.

Example: Broad bag straps are more comfortable because the weight is spread over a larger area.

Liquid pressure: Liquids exert pressure on the bottom as well as the sides of a container.

Height of liquid: Pressure exerted by a liquid increases as the height of the liquid column increases.

Atmospheric pressure: The pressure exerted by the air around us is called atmospheric pressure.

Wind: Air moves from a region of high pressure to a region of low pressure.

Warm air: Warm air rises and creates a low-pressure area.

Sea breeze: During the day, land heats faster. Warm air rises over land and air moves from the sea towards land.

Land breeze: At night, land cools faster. Air moves from land towards the sea.

High-speed wind: High-speed winds are accompanied by lower air pressure.

Storm: Strong winds accompanied by rain are called a storm.

Thunderstorm: A storm accompanied by lightning and thunder is called a thunderstorm.

Lightning: A sudden flow of electric charges produces a bright flash of light called lightning.

Thunder: Lightning heats the surrounding air. The air expands and produces the sound called thunder.

Cyclone: A cyclone is a spinning system of clouds, winds and rain formed around a very low-pressure area.

Eye of cyclone: The centre of a cyclone has the lowest pressure. The wind is relatively calm there.

Lightning conductor: It provides an easy path for electric charges to reach the ground safely.

3. Important Formulae and Units

Pressure = Force / Area

Quantity	SI Unit
Force	Newton (N)
Area	m²
Pressure	N/m² or Pascal (Pa)

Remember: 1 Pa = 1 N/m².

Air pressure: Air pressure may also be expressed in millibar (mb) and hectopascal (hPa). 1 mb = 100 Pa and 1 hPa = 100 Pa.

4. Activity Questions

Activity 6.1 – Liquid Pressure

Do both balloons bulge? Do they bulge to the same extent?

Yes. They bulge to nearly the same extent when the heights of the water columns are equal.

What will happen to the bulge of the balloon if we increase the height of the water column?

The balloon will bulge more because liquid pressure increases with the height of the liquid column.

Activity 6.2 – Pressure on Container Walls

What do you observe?

Water flows out through all the holes in the sides of the bottle.

What can you infer from this observation?

Liquids exert pressure on the sides of containers as well as on the bottom.

Activity 6.3 – Pressure Exerted by Air

In which case is the lifting easier, with the folded or the unfolded chart paper covering the paper plate?

Lifting is easier with the folded chart paper because it covers a smaller area.

What can you infer from this?

Air exerts pressure on the chart paper and the pressure effect increases with the area.

Activity 6.4 – Rubber Sucker

Do you realise that it sticks to the surface?

Yes. The sucker sticks because the pressure outside is greater than the pressure inside it.

Now, try to pull it off. Do you find it difficult to pull it off?

Yes. A force is needed to overcome the pressure difference.

Activity 6.5 – Movement of Air

Predict what would happen to the balloons.

Air will move from the inflated balloon to the uninflated balloon.

Observe what happens to both the balloons. Did it happen as predicted?

Yes. The inflated balloon becomes smaller and the other balloon becomes bigger.

Do you observe any change in the size of the balloons? Write down your observations.

Yes. Air moves from high pressure to low pressure until the pressure becomes nearly equal.

How do winds form?

Winds form because air moves from a region of high pressure to a region of low pressure.

Does the difference in air pressure have anything to do with the formation of winds?

Yes. Greater pressure differences can produce stronger winds.

Activity 6.6 – High-Speed Winds

What happens to the balloons?

The balloons move towards each other.

Now blow harder and observe.

The balloons move towards each other more quickly.

What can you infer from this activity?

High-speed winds are accompanied by reduced air pressure.

5. Important Questions from the Chapter

Suppose you are living on the second floor of a three-storeyed building and an overhead water tank is placed on the top floor. Will you or your friend on the first floor receive a more powerful stream of tap water? Give reasons.

The friend on the first floor will receive a more powerful stream because the water column above that floor is taller.

Do liquids also exert pressure on the walls of the container?

Yes. Liquids exert pressure on the walls as well as the bottom of a container.

You must have seen water spurting out like a fountain from leaking joints or holes in water pipes. Can you explain why this happens? Is it due to the pressure exerted by water on the walls of the pipes?

Yes. Water exerts pressure on the walls of pipes, so water comes out through holes or leaks.

What happens when an inflated balloon is kept without closing its mouth? The air escapes from the balloon. Why does the air escape from the balloon?

Air escapes because the pressure inside the balloon is higher than the surrounding air pressure.

Why are roofs sometimes blown away during storms?

High-speed wind creates lower pressure above the roof. The higher pressure inside can push the roof upward.

Why is it safer to keep doors and windows of the houses open during storms with high-speed winds?

Opening them reduces the pressure difference between inside and outside, helping to protect the roof.

Have you heard the sound of thunder and seen lightning during the rainy season?

Yes. Thunder and lightning commonly occur during thunderstorms.

Have you ever wondered how large the atmospheric pressure is?

Atmospheric pressure is very large. Air pressure on a 15 cm × 15 cm area can produce a force of about 2250 N.

6. Lightning Safety

Important Safety Rules During Lightning:

Stay away from tall objects.
Move to a low-lying open area when safe to do so.
Crouch down and minimise contact with the ground.
Do not lie flat on the ground.
Avoid umbrellas with metallic rods.
If you are in water, get out.
Inside a bus or car is comparatively safer.

What is a lightning conductor?

A lightning conductor is a metal rod that provides an easy path for electric charges to pass safely into the ground.

7. Cyclone – Easy Concept

Warm ocean water → Warm moist air rises → Low pressure → More air rushes in → Air rises and spins → Cyclone

Cyclones generally form over warm ocean waters.

Warm, moist air rises and creates a low-pressure area.

Water vapour condenses and releases heat, causing the rising air to become warmer and rise further.

Air from surrounding areas moves towards the low-pressure region.

Earth’s rotation causes the moving air to spin.

The centre of the cyclone is called the eye.

The eye has the lowest pressure and relatively calm winds.

Cyclones become weaker after moving over land because their supply of warm moist air from the ocean is cut off.

Cyclones can cause strong winds, heavy rainfall, storm surges, floods, landslides, power failures and damage to buildings and crops.

8. Snapshots – Quick Revision

Pressure

Force per unit area.

Unit

N/m² or pascal (Pa).

Liquid Pressure

Liquids exert pressure on the bottom and sides.

Atmospheric Pressure

Pressure exerted by air around us.

Wind

Air moves from high pressure to low pressure.

Warm Air

Warm air rises and creates low pressure.

Thunderstorm

A storm with lightning and thunder.

Lightning

A sudden flow of electric charges.

Lightning Conductor

Provides a safe path for electric charges to the ground.

Cyclone

A rotating system around a very low-pressure area.

9. Keep the Curiosity Alive – Book Questions

1. Choose the correct statement.

(i) Look at Fig. 6.21 carefully. Vessel R is filled with water. When pouring of water is stopped, the level of water will be ____________________.

(a) the highest in vessel P

(b) the highest in vessel Q

(d) equal in all three vessels

Answer: (d) equal in all three vessels.

(ii) A rubber sucker (M) is pressed on a flat smooth surface and an identical sucker (N) is pressed on a rough surface:

(a) Both M and N will stick to their surfaces.

(b) Both M and N will not stick to their surfaces.

(d) M will not stick but N will stick.

Answer: (c) M will stick but N will not stick.

(iii) A water tank is placed on the roof of a building at a height ‘H’. To get water with more pressure on the ground floor, one has to

(a) increase the height ‘H’ at which the tank is placed.

(b) decrease the height ‘H’ at which the tank is placed.

(d) replace the tank with another tank of the same height that can hold less water.

Answer: (a) increase the height ‘H’ at which the tank is placed.

(iv) Two vessels, A and B contain water up to the same level as shown in Fig. 6.22. PA and PB is the pressure at the bottom of the vessels. FA and FB is the force exerted by the water at the bottom of the vessels.

(a) PA = PB, FA = FB

(b) PA = PB, FA <FB

(d) PA > PB, FA > FB

Answer: (b) PA = PB, FA < FB.

2. State whether the following statements are True [T] or False [F].

(i) Air flows from a region of higher pressure to a region of lower pressure. [ ]

Answer: True [T]

(ii) Liquids exert pressure only at the bottom of a container. [ ]

Answer: False [F]

(iii) Weather is stormy at the eye of a cyclone. [ ]

Answer: False [F]

(iv) During a thunderstorm, it is safer to be in a car. [ ]

Answer: True [T]

3. Fig. 6.23 a shows a boy lying horizontally, and Fig. 6.23b shows the boy standing vertically on a loose sand bed. In which case does the boy sink more in sand? Give reasons.

The boy sinks more when standing vertically because his weight acts over a smaller area, producing greater pressure.

4. An elephant stands on four feet. If the area covered by one foot is 0.25 m2, calculate the pressure exerted by the elephant on the ground if its weight is 20000 N.

Total area = 4 × 0.25 = 1 m².
Pressure = Force ÷ Area = 20000 ÷ 1 = 20000 Pa.

Prepare some questions based on your learnings so far …

Example: Why does warm air rise? Why do winds move from high pressure to low pressure?

Reflect on the questions framed by your friends and try to answer …

Students should discuss their friends’ questions and answer them using the concepts learned in the chapter.

5. There are two boats, A and B. Boat A has a base area of 7 m2, and 5 persons are seated in it. Boat B has a base area of 3.5 m2, and 3 persons are seating in it. If each person has a weight of 700 N, find out which boat will experience more pressure on its base and by how much?

Boat A: Force = 5 × 700 = 3500 N.
Pressure = 3500 ÷ 7 = 500 Pa.

Boat B: Force = 3 × 700 = 2100 N.
Pressure = 2100 ÷ 3.5 = 600 Pa.

Boat B experiences more pressure by 100 Pa.

6. Would lightning occur if air and clouds were good conductors of electricity? Give reasons for your answer.

No. If air were a good conductor, charges would flow away gradually instead of building up and suddenly producing lightning.

7. What will happen to the two identical balloons A and B as shown in Fig. 6.24 when water is filled into the bottle up to a certain height. Will both the balloons bulge? If yes, will they bulge equally? Explain your answer.

Both balloons can bulge because water exerts pressure on the walls. If they are at the same height, they will experience equal pressure and bulge similarly.

8. Explain how a storm becomes a cyclone.

Over warm ocean water, warm moist air rises and creates very low pressure. More air rushes in, rises and begins to spin due to Earth’s rotation. This develops into a cyclone.

9. Fig. 6.25 shows trees along the sea coast in a summer afternoon. Identify which side is land— A or B. Explain your answer.

The side where the trees bend towards the land indicates the direction of the sea breeze. During the afternoon, land heats faster, so air moves from sea towards land.

10. Describe an activity to show that air flows from a region of high pressure to a region of low pressure.

Connect an inflated balloon and an uninflated balloon using a straw. Air moves from the inflated balloon, where pressure is higher, towards the uninflated balloon, where pressure is lower.

11. What is a thunderstorm? Explain the process of its formation.

A thunderstorm is a storm with lightning and thunder. Warm moist air rises, cools and forms clouds. Strong upward and downward winds help charges develop in the clouds. Their discharge produces lightning and thunder.

12. Explain the process that causes lightning.

Strong winds cause water droplets and ice particles to rub against each other. Electric charges build up in clouds. When the charges suddenly flow, a bright flash called lightning is produced.

13. Explain why holes are made in banners and hoardings.

Holes allow air to pass through. This reduces the pressure force on the banner and helps prevent it from tearing or being blown away.

10. Discover, Design, and Debate

Hold a strip of paper, 18 cm long and 2 cm wide, between your thumb and forefinger so that it hangs freely. Predict what you will observe if you blow over the paper. Perform the activity now. Note down your observations and interpret your results.

When air is blown over the paper, the paper rises towards the blown air. The fast-moving air creates lower pressure above the paper, while the higher pressure below pushes it upward.

List three major cyclones which have occured in India in the last 20 years. List two major destruction caused by each of the cyclones. What measures were taken by the local government and communities to reduce the loss of life and destruction of property? Mention two suggestions you would like to propose to the local government.

This is a research activity. Students should collect information from reliable weather and government sources and prepare a table of cyclones, damage, safety measures and suggestions.

Collect data on the strength of thunderstorms for various regions of India. Compare your findings and identify which regions are more prone to thunderstorms. Can you give reasons for your findings?

This is a research activity. Students should collect weather data, compare different regions and relate thunderstorm activity to factors such as heat, moisture and atmospheric conditions.

11. Super Quick Revision

1. Pressure = Force ÷ Area.

2. Smaller area gives greater pressure for the same force.

3. Liquids exert pressure in all directions.

4. Liquid pressure increases with the height of the liquid column.

5. Air exerts atmospheric pressure.

6. Air moves from high pressure to low pressure.

7. Warm air rises and creates low pressure.

8. High-speed winds are associated with lower pressure.

9. A storm is strong wind accompanied by rain.

10. A thunderstorm has lightning and thunder.

11. Lightning is caused by sudden flow of electric charges.

12. A lightning conductor protects buildings.

13. Cyclones form over warm ocean waters.

14. The eye is the calm centre of a cyclone.

15. Cyclones weaken over land because their supply of warm moist ocean air is cut off.

Prepare with this NCERT Curiosity worksheet for Chapter 6 The worksheet includes important questions and revision exercises to help students understand key concepts, practise what they have learned, and prepare effectively for class tests and exams.

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Class 8 Science Chapter 6 – Pressure, Winds, Storms, and Cyclones | NCERT Curiosity Notes & Book Solutions