Pressure, Winds, Storms, and Cyclones – Important Questions and Answers
Premium CBSE Class 8 Science revision post based on the chapter Pressure, Winds, Storms, and Cyclones. Includes important concepts, keywords, exam-style questions, case studies, assertion-reason, competency questions, HOTS, diagram-based questions, FAQs, and an interactive quiz.
Short Introduction
Pressure, winds, storms, and cyclones are closely connected. Wind can exert force and create wind pressure. Air moves from regions of high pressure to regions of low pressure. This movement of air produces winds. Strong winds, moisture, pressure differences, lightning, and Earth’s rotation together explain thunderstorms and cyclones. This chapter helps students understand these natural events scientifically and safely.
Chapter Overview
Pressure
Pressure is force per unit area. It increases when force increases or area decreases.
Liquid Pressure
Liquids exert pressure at the bottom and on the walls of containers in all directions.
Atmospheric Pressure
Air around us exerts pressure on all objects. This is called atmospheric pressure.
Formation of Wind
Air moves from high-pressure regions to low-pressure regions, causing winds.
Storms and Lightning
Storms form due to rising warm moist air. Lightning occurs due to sudden flow of charges.
Cyclones
Cyclones are large spinning storms formed over warm ocean waters with very low pressure at the centre.
Important Keywords with Meanings
| Keyword | Meaning |
|---|---|
| Pressure | Force acting per unit area on a surface. |
| Pascal | SI unit of pressure, denoted by Pa. 1 Pa = 1 N/m². |
| Force | A push or pull acting on an object. |
| Area | The surface over which force is applied. |
| Liquid pressure | Pressure exerted by a liquid at the bottom and on the walls of a container. |
| Water column | The height of water in a container or pipe. |
| Atmosphere | The envelope of air surrounding the Earth. |
| Atmospheric pressure | Pressure exerted by the air around us. |
| Millibar | A practical unit of air pressure. 1 millibar = 100 Pa. |
| Hectopascal | A unit of air pressure. 1 hPa = 100 Pa. |
| Wind | Moving air caused by pressure differences. |
| Low pressure area | A region where air pressure is lower than surrounding regions. |
| High pressure area | A region where air pressure is higher than surrounding regions. |
| Sea breeze | Wind blowing from sea to land during the day. |
| Land breeze | Wind blowing from land to sea at night. |
| Storm | Strong winds accompanied by rain, hail, or snow. |
| Thunderstorm | A storm accompanied by thunder and lightning. |
| Lightning | A bright flash of light produced by sudden flow of electric charges. |
| Thunder | Loud sound produced when lightning rapidly heats air and makes it expand. |
| Lightning conductor | A metallic rod that provides an easy path for electric charges to pass into the ground. |
| Cyclone | A large spinning storm formed over warm ocean waters. |
| Eye of cyclone | The calm central region of lowest pressure in a cyclone. |
| Storm surge | A wall of ocean water pushed towards the shore by strong cyclone winds. |
| IMD | India Meteorological Department, which monitors cyclones and thunderstorms in India. |
Important Formula
SI unit of pressure = N/m² = pascal = Pa
Very Short Answer Questions
1. What is pressure?
Answer: Pressure is force acting per unit area.
2. Write the formula for pressure.
Answer: Pressure = Force ÷ Area.
3. What is the SI unit of pressure?
Answer: The SI unit of pressure is newton per metre square or pascal.
4. What is the symbol of pascal?
Answer: The symbol of pascal is Pa.
5. What happens to pressure when area decreases?
Answer: Pressure increases when area decreases.
6. Why are school bags with broad straps comfortable?
Answer: Broad straps increase the area of contact and reduce pressure on shoulders.
7. Why is a sharp knife better for cutting?
Answer: A sharp knife has a smaller contact area, so it produces greater pressure.
8. Do liquids exert pressure?
Answer: Yes, liquids exert pressure.
9. In which directions do liquids exert pressure?
Answer: Liquids exert pressure in all directions.
10. On what does pressure exerted by a liquid depend?
Answer: It depends on the height of the liquid column.
11. Why are overhead water tanks placed at a height?
Answer: They are placed at a height to increase water pressure in taps.
12. What is atmosphere?
Answer: The envelope of air surrounding the Earth is called atmosphere.
13. What is atmospheric pressure?
Answer: The pressure exerted by air around us is called atmospheric pressure.
14. Why are we not crushed by atmospheric pressure?
Answer: The pressure inside our body balances the atmospheric pressure outside.
15. How does air move?
Answer: Air moves from a region of high pressure to a region of low pressure.
16. What causes wind?
Answer: Difference in air pressure causes wind.
17. What happens to pressure when wind speed increases?
Answer: High-speed winds are accompanied by reduced air pressure.
18. What is a storm?
Answer: Strong winds accompanied by rain, hail, or snow are called a storm.
19. What is a thunderstorm?
Answer: A storm accompanied by lightning and thunder is called a thunderstorm.
20. What is lightning?
Answer: Lightning is a bright flash of light caused by sudden flow of electric charges.
21. What is thunder?
Answer: Thunder is the loud sound produced due to rapid expansion of air heated by lightning.
22. What is a cyclone?
Answer: A cyclone is a large spinning storm formed over warm ocean waters.
23. What is the eye of a cyclone?
Answer: The eye is the calm central region of lowest pressure in a cyclone.
24. Which department monitors cyclones in India?
Answer: The India Meteorological Department, or IMD, monitors cyclones in India.
Short Answer Questions
1. Why do broad straps of a bag reduce pain on the shoulders?
Answer: Broad straps spread the weight of the bag over a larger area. Since pressure decreases when area increases, the pressure on shoulders becomes less and the bag feels more comfortable.
2. Why is it easier to drive a nail from its pointed end?
Answer: The pointed end has a smaller area. For the same force, smaller area produces greater pressure, making it easier to drive the nail into a surface.
3. Why do people place a round cloth under heavy loads carried on the head?
Answer: The cloth increases the area over which the load acts. This reduces pressure on the head and makes carrying the load more comfortable.
4. Why are overhead water tanks placed at a height?
Answer: Liquid pressure increases with the height of the water column. A tank placed at a height creates more pressure, giving a stronger stream of water from taps.
5. What does the balloon experiment with water-filled pipes show?
Answer: It shows that liquid pressure at the bottom depends on the height of the water column, not on the diameter of the pipe.
6. How does water exert pressure on the walls of a container?
Answer: When holes are made in the sides of a bottle filled with water, water flows out through them. This shows that water exerts pressure on the side walls of the container.
7. Why is the base of a dam made broader than its top?
Answer: Water pressure increases with depth. The pressure near the bottom of a dam is very large, so the base is made broad and strong to withstand it.
8. What is atmospheric pressure?
Answer: Atmospheric pressure is the pressure exerted by the air surrounding the Earth on all objects.
9. Why does a rubber sucker stick to a smooth surface?
Answer: When the sucker is pressed, most air inside it is pushed out. The outside atmospheric pressure becomes greater than the pressure inside, so the sucker sticks to the surface.
10. How is wind formed?
Answer: Wind is formed when air moves from a high-pressure region to a low-pressure region. Pressure differences are often produced by unequal heating of land and water.
11. Explain sea breeze.
Answer: During the day, land heats faster than sea. Warm air above land rises and creates low pressure. Cooler air from the high-pressure region over the sea moves towards land, forming sea breeze.
12. Explain land breeze.
Answer: At night, water remains warmer than land. Warm air over the sea rises, creating low pressure. Air from the land moves towards the sea, forming land breeze.
13. Why can high-speed winds blow off roofs?
Answer: High-speed winds create low pressure above roofs. The pressure inside the house may become greater than the pressure above the roof. If the pressure difference is large, the roof may be blown off.
14. Why is it safer to keep doors and windows open during storms with high-speed winds?
Answer: Open doors and windows allow wind to pass through the house. This reduces the pressure difference between inside the house and above the roof, reducing the chance of the roof being blown off.
15. What safety precautions should be taken during lightning?
Answer: Stay away from tall objects, avoid umbrellas with metallic rods, get out of water, crouch in a low-lying open area, do not lie flat, and stay inside a car or bus if possible.
Long Answer Questions
1. Define pressure and explain its daily-life applications.
Answer: Pressure is defined as force per unit area.
- Pressure = Force ÷ Area.
- Its SI unit is N/m², also called pascal.
- Broad straps of bags reduce pressure on shoulders.
- A sharp knife cuts easily because its edge has a small area and produces high pressure.
- A pointed nail enters a surface easily because pressure is high at the pointed end.
- A cloth pad under head loads reduces pressure by increasing area.
2. Explain how liquids exert pressure.
Answer: Liquids exert pressure at the bottom and on the walls of a container. The pressure increases with the height of the liquid column. In a pipe with water and a balloon tied at the bottom, the balloon bulges due to pressure exerted by water. If the height of water is increased, the balloon bulges more. Holes made in the sides of a water-filled bottle show that liquids exert pressure sideways also. Therefore, liquids exert pressure in all directions.
3. Why are dams built with broad bases?
Answer: Water stored in a dam exerts pressure on the walls and base. Liquid pressure increases with depth, so water pressure is much greater near the bottom. A broad base helps the dam withstand this large horizontal pressure and supports the structure strongly.
4. Explain atmospheric pressure with the rubber sucker activity.
Answer: When a rubber sucker is pressed against a smooth surface, most air between the sucker and the surface is pushed out. The air pressure inside the sucker becomes less than the atmospheric pressure outside. The greater outside pressure pushes the sucker against the surface, making it stick. To remove it, we must apply enough force to overcome this pressure difference.
5. How are winds formed?
Answer: Winds are formed due to differences in air pressure. Air moves from a region of high pressure to a region of low pressure. When air gets heated, it becomes lighter and rises, creating a low-pressure area. Cooler air from surrounding high-pressure areas rushes in to take its place. This movement of air is called wind.
6. Explain why high-speed winds are accompanied by low pressure.
Answer: When air moves at high speed, the pressure in that region becomes lower. This can be shown by blowing air between two hanging balloons. The balloons move towards each other because the fast-moving air between them creates low pressure, while higher pressure outside pushes them inward.
7. Explain the formation of a storm.
Answer: When land gets heated, warm and moist air rises because it is lighter. This creates a low-pressure area. Cooler air from surrounding high-pressure areas flows in and also gets heated and rises. The rising air cools at greater heights, and moisture condenses to form clouds. Water droplets combine to form heavier drops that fall as rain, hail, or snow. Strong winds with rain form a storm.
8. Explain the process of lightning and thunder.
Answer: Strong winds moving upward and downward in clouds cause rubbing between water droplets and ice particles. This produces static electric charges. Lighter positively charged ice particles move upward, while heavier negatively charged water droplets occupy the lower part of clouds. When charge buildup becomes very large, air loses its insulating property and charges suddenly flow, producing lightning. Lightning rapidly heats air, causing it to expand and produce the loud sound called thunder.
9. Describe the formation of a cyclone.
Answer: Cyclones form over warm ocean waters. Warm moist air above the ocean rises and creates a low-pressure area. As water vapour condenses into raindrops, heat is released into the atmosphere. This makes the rising air warmer and causes it to rise further, creating even lower pressure. Surrounding air rushes in and starts rising. Due to Earth’s rotation, the moving air begins to spin. This repeated cycle forms a spinning system of clouds, winds, and rain called a cyclone.
10. What damage can cyclones cause and how can we stay safe?
Answer: Cyclones can cause strong winds, heavy rainfall, storm surges, floods, landslides, blocked roads, power failures, contaminated drinking water, and damage to farmland. To stay safe, people should follow IMD warnings, track weather reports, keep emergency kits ready, move to cyclone shelters, avoid coastal areas during warnings, and cooperate with local authorities.
Case-Study Based Questions
Case Study 1: Bag Straps and Pressure
Pawan and Megha carry bags of equal weight. Pawan’s bag has narrow straps and hurts his shoulders, while Megha’s bag has broad straps and feels comfortable.
Q1. Why does Pawan feel more pain?
Answer: Narrow straps act over a smaller area, so they exert greater pressure on the shoulders.
Q2. How do broad straps help?
Answer: Broad straps increase the area of contact and reduce pressure.
Q3. Which formula explains this?
Answer: Pressure = Force ÷ Area.
Case Study 2: Overhead Water Tank
An overhead water tank is placed on the top of a building. A student on the first floor gets a stronger water stream than a student on the second floor.
Q1. Why does the first floor receive stronger water flow?
Answer: The water column height above the first floor is greater, so water pressure is higher.
Q2. What happens if the tank is placed higher?
Answer: Water pressure in the taps increases.
Q3. What does this show about liquid pressure?
Answer: Liquid pressure depends on the height of the liquid column.
Case Study 3: Balloons Connected by a Straw
One balloon is inflated and connected to an uninflated balloon through a straw. Air moves from the inflated balloon to the uninflated balloon until both become almost equal in size.
Q1. Why does air move from one balloon to the other?
Answer: Air moves from the high-pressure inflated balloon to the low-pressure uninflated balloon.
Q2. When does the flow of air stop?
Answer: Air flow stops when pressure in both balloons becomes equal.
Q3. Which natural phenomenon is explained by this activity?
Answer: Formation of wind due to pressure difference.
Case Study 4: Roofs During Storms
During a storm, high-speed winds blow over weak roofs. Sometimes roofs are blown off.
Q1. Why can roofs be blown away?
Answer: High-speed winds create low pressure above the roof. Higher pressure below the roof can push it upward.
Q2. Why should doors and windows be kept open during such storms?
Answer: This reduces the pressure difference between inside the house and above the roof.
Q3. What principle is involved?
Answer: High-speed winds are accompanied by lower pressure.
Case Study 5: Lightning Safety
A group of students is outside during a thunderstorm. They see lightning and hear thunder.
Q1. What should they avoid?
Answer: They should avoid tall objects, water bodies, metallic umbrellas, and lying flat on the ground.
Q2. What is a safer position in an open area?
Answer: They should crouch down in a low-lying open area and minimise contact with the ground.
Q3. Why is lightning dangerous?
Answer: It can cause fires, damage buildings, severe burns, and death in humans and animals.
Assertion-Reason Questions
Choose the correct option:
A. Both Assertion and Reason are true and Reason is the correct explanation.
B. Both Assertion and Reason are true but Reason is not the correct explanation.
C. Assertion is true but Reason is false.
D. Assertion is false but Reason is true.
1. Assertion: Broad straps of bags are more comfortable. Reason: Broad straps reduce pressure by increasing area.
Answer: A
2. Assertion: A sharp knife cuts better than a blunt knife. Reason: A sharp edge has smaller area and produces greater pressure.
Answer: A
3. Assertion: Liquids exert pressure only at the bottom. Reason: Liquids do not exert pressure on the walls of containers.
Answer: Both Assertion and Reason are false. Liquids exert pressure in all directions.
4. Assertion: Water pressure increases with height of water column. Reason: Higher water column produces greater pressure at the bottom.
Answer: A
5. Assertion: Dams have broad bases. Reason: Water pressure near the bottom of a dam is very large.
Answer: A
6. Assertion: A rubber sucker sticks better on a smooth surface. Reason: A smooth surface helps create a pressure difference.
Answer: A
7. Assertion: Air moves from low pressure to high pressure. Reason: Wind forms due to pressure differences.
Answer: D
8. Assertion: High-speed winds can blow away weak roofs. Reason: High-speed winds produce low pressure above roofs.
Answer: A
9. Assertion: Thunder is heard after lightning is seen. Reason: Lightning rapidly heats air and causes it to expand, producing sound.
Answer: A
10. Assertion: The eye of a cyclone is calm. Reason: The lowest pressure region is at the centre of a cyclone.
Answer: A
Competency-Based and Critical Thinking / HOTS Questions
1. A boy lies on loose sand and then stands on it. In which case will he sink more?
Answer: He will sink more when standing because the same weight acts on a smaller area of the feet, producing greater pressure.
2. An elephant stands on four feet. If one foot covers 0.25 m² and its weight is 20000 N, calculate pressure.
Answer: Total area = 4 × 0.25 = 1 m². Pressure = 20000 ÷ 1 = 20000 Pa.
3. Boat A has base area 7 m² and carries 5 persons. Boat B has base area 3.5 m² and carries 3 persons. Each person weighs 700 N. Which boat experiences more pressure?
Answer: Boat A pressure = 3500 ÷ 7 = 500 Pa. Boat B pressure = 2100 ÷ 3.5 = 600 Pa. Boat B experiences more pressure by 100 Pa.
4. Why do holes in banners and hoardings prevent damage during strong winds?
Answer: Holes allow air to pass through, reducing pressure difference across the banner. This reduces the force exerted by wind and prevents tearing or falling.
5. Would lightning occur if air and clouds were good conductors of electricity?
Answer: Lightning would not build up in the same way because charges would flow continuously through conducting air instead of accumulating until sudden discharge occurs.
6. Why does a rubber sucker not stick well on a rough surface?
Answer: A rough surface allows air to remain or enter between the sucker and the surface. A proper pressure difference is not formed, so the sucker does not stick well.
7. Why are cyclones weaker after reaching land?
Answer: Once a cyclone reaches land, its supply of warm moist air from the ocean is cut off. Without this energy source, it gradually loses strength.
8. If high-speed winds move over a paper strip, why does the paper rise?
Answer: Fast-moving air above the paper creates low pressure. Higher pressure below the paper pushes it upward.
9. Why are cyclones more common over warm oceans?
Answer: Warm oceans provide heat and moisture. Warm moist air rises and condenses, releasing heat and strengthening the low-pressure system needed for cyclone formation.
10. Why do weather satellites help reduce cyclone damage?
Answer: Satellites help track cyclone location and predict its path. Early warnings allow evacuation, emergency preparation, and movement to cyclone shelters.
Diagram-Based Questions
Diagram 1: Pressure Formula
Question: What happens to pressure if the same force acts on a smaller area?
Answer: Pressure increases.
Diagram 2: Liquid Pressure and Height
Question: Why does the balloon bulge more when water height increases?
Answer: Greater water column height produces greater pressure at the bottom.
Diagram 3: Formation of Wind
Question: In which direction does air flow?
Answer: Air flows from high pressure to low pressure.
Diagram 4: Thunderstorm Formation
Question: What causes lightning?
Answer: Sudden flow of large accumulated electric charges causes lightning.
Diagram 5: Cyclone
Question: What is the eye of a cyclone?
Answer: The eye is the calm central region of lowest pressure in a cyclone.
Quick Revision Box
- Pressure = Force ÷ Area.
- SI unit of pressure is N/m² or pascal.
- Broad straps reduce pressure by increasing area.
- Sharp tools increase pressure by reducing area.
- Liquids exert pressure in all directions.
- Liquid pressure increases with height of liquid column.
- Air around us exerts atmospheric pressure.
- Air moves from high pressure to low pressure.
- Pressure differences cause winds.
- High-speed winds are accompanied by low pressure.
- Storms are strong winds accompanied by rain, hail, or snow.
- Lightning occurs due to sudden flow of electric charges.
- Thunder is produced by rapid expansion of heated air.
- Cyclones form over warm ocean waters.
- The eye of a cyclone is calm and has the lowest pressure.
- IMD monitors cyclones and thunderstorms in India.
Important Exam Tips
Interactive Quiz
Choose the correct answer and click submit.
Frequently Asked Questions
1. What is pressure?
Pressure is the force acting per unit area on a surface.
2. What is the SI unit of pressure?
The SI unit of pressure is newton per metre square, also called pascal.
3. Why do sharp tools work better?
Sharp tools have a smaller contact area, so they produce greater pressure for the same force.
4. Do liquids exert pressure sideways?
Yes, liquids exert pressure at the bottom and on the walls of a container in all directions.
5. Why are water tanks placed at a height?
Water tanks are placed at a height because liquid pressure increases with the height of the water column.
6. What causes wind?
Wind is caused by air moving from high-pressure regions to low-pressure regions.
7. Why can high-speed winds blow away roofs?
High-speed winds create low pressure above roofs. Higher pressure inside can push the roof upward and blow it away.
8. What is a thunderstorm?
A thunderstorm is a storm accompanied by lightning and thunder.
9. What is the eye of a cyclone?
The eye of a cyclone is the calm central region of lowest pressure.
10. How can we stay safe during cyclones?
Follow IMD warnings, keep an emergency kit, move to cyclone shelters, avoid unsafe areas, and listen to local authorities.
Final Conclusion
The chapter Pressure, Winds, Storms, and Cyclones shows how pressure affects everyday life and large natural events. Pressure depends on force and area, liquids and gases exert pressure, wind forms due to pressure differences, and extreme pressure systems can lead to storms and cyclones. Understanding these concepts helps us explain weather events and follow safety measures during thunderstorms and cyclones.
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