Pressure, Winds, Storms, and Cyclones | CBSE Class 8 Science Notes

This note covers pressure and contact area, pressure in liquids and air, wind formation, sea and land breezes, the effects of fast-moving air, storms, lightning, thunderstorms, cyclone formation, cyclone damage, and protective measures.

What is pressure, and how is it calculated?

A force is a push or pull. Its effect on a surface depends on the area over which it acts. Pressure is the force acting per unit area. Here, the force considered acts perpendicular to the surface, meaning at right angles to it.

Definition: Pressure is force per unit area. For a force acting perpendicular to a surface, pressure is calculated by dividing that force by the area over which it acts.

Pressure = Force / Area

In this equation, force means the perpendicular force, area means the surface area over which it acts, and the slash means division. The SI, or International System of Units, provides the units used to express these quantities.

Which units express force, area, and pressure?

1 Pa = 1 N/m². A pressure of one pascal corresponds to a force of one newton acting over one square metre. Pressure and force are different quantities: pressure includes the area over which the force acts.

Worked example 1. A perpendicular force of 100 N acts over cardboard of area 2 m². Calculate the pressure. Formula: Pressure = Force / Area. Substitute: 100 N / 2 m². Answer: The pressure is 50 N/m², or 50 Pa.

The calculation uses both the force and the area. Writing the force alone does not give the pressure. Keep the unit with the answer so that a value describing force is not confused with a value describing pressure.

How does contact area change pressure in everyday situations?

Contact area is the area over which one object presses against another. For the same force, a smaller contact area produces greater pressure. Spreading that force over a larger area reduces the pressure. The weight of a load is the force due to gravity, the pull of Earth on that load.

Two equally heavy bags can feel different on the shoulders. A narrow strap concentrates the bag's weight over a smaller area. A broad strap spreads the same weight over a larger area and reduces pressure, making the bag more comfortable to carry.

When is lower pressure useful?

A water-filled bucket is easier to lift with a broad handle than a narrow handle. The broader handle increases the area over which the weight acts. The same principle explains the round piece of cloth that people often place under loads carried on their heads.

When is higher pressure useful?

The pointed end of a nail and the sharp edge of a knife make use of smaller areas. A nail enters more easily through its point, and a sharp knife cuts an apple more easily than a blunt edge.

Note: Comparisons based on contact area require the applied force to remain the same. A broad strap reduces pressure; it does not reduce the weight of the bag. Activities involving nails or knives require adult supervision.

How can pressure calculations include several supporting surfaces?

When a load is supported over several contact surfaces, the pressure calculation needs the total supporting area, meaning the combined area over which the force acts. Using the area of just one contact surface can give an incorrect result for the whole load.

How is the pressure beneath an elephant calculated?

Worked example 2. An elephant stands on four feet. Each foot covers 0.25 m², and the elephant's weight is 20000 N. Find the pressure on the ground. Formula: Total area = Number of feet × Area of one foot; Pressure = Weight / Total area. Here × means multiplication. Substitute: Total area = 4 × 0.25 m² = 1 m². Answer: Pressure = 20000 N / 1 m² = 20000 Pa.

All four feet contribute to the area supporting the elephant's weight. The weight already gives the force in newtons, so no conversion from mass is required. The important steps are finding the combined area and then dividing the weight by that area.

How can two boats be compared?

Worked example 3. Boat A has a base area of 7 m² and carries five people. Boat B has a base area of 3.5 m² and carries three people. Each person weighs 700 N. Compare the pressure due to the people over each boat's base. Formula: Total weight = Number of people × Weight per person; Pressure = Total weight / Base area. Answer: Boat A: 5 × 700 N = 3500 N, giving 3500 N / 7 m² = 500 Pa. Boat B: 3 × 700 N = 2100 N, giving 2100 N / 3.5 m² = 600 Pa. Boat B has 100 Pa more pressure due to its passengers.

The letters A and B identify the two boats. Although boat A carries more people, boat B has the greater pressure from its passengers because its smaller base area also enters the calculation. Compare both weight and area, rather than passenger number alone.

How does the height of water affect liquid pressure?

Liquids exert pressure. A water column is the vertical body of water above the point being considered. The pressure at the bottom increases when the height of water above it increases. This can be investigated using pipes and rubber balloons.

What happens with equal water heights?

1. Take two transparent pipes of the same length, about 25 centimetres. A centimetre, written cm, is one hundredth of a metre. Use pipes of different diameters, meaning different widths across their circular openings.
2. Attach a good-quality rubber balloon to one end of each pipe and clamp both pipes upright on a stand.
3. Fill both pipes to the same water level, about halfway up.
4. Compare the balloons. They bulge to the same extent, even though the wider pipe contains a greater weight of water.

The equal bulges show that equal water-column heights produce equal pressure in this arrangement. The different weights of water do not explain the bulging. The crucial comparison is between the heights of water above the balloons.

Two upright pipes are held on stands. One is labelled narrow pipe and the other broad pipe. Water reaches the same height in both, and balloons attached at the bottom show equal bulges.

See Fig. 6.5 in your NCERT textbook

What changes when more water is added?

Adding water to one pipe increases the height of its water column. The balloon at its bottom bulges more because the pressure increases. Repeating the addition links the increasing height with the increasing bulge.

Overhead tanks are water-storage tanks placed at a height. Their height increases the water pressure at taps, producing a good stream. Raising the water column increases pressure; simply choosing a wider container at the same water height does not establish a greater bottom pressure.

Do liquids exert pressure on the sides of containers?

Liquid pressure acts on the sides as well as the bottom of a container. Water flowing through holes in a bottle provides visible evidence. The water does not need an opening in the base to escape under pressure.

What does a bottle with side holes show?

1. Use a plastic bottle with its cap removed and four small holes around its sides near the bottom.
2. Keep all the holes at the same height from the bottom, and cover them with tape.
3. Fill the bottle with water, then remove the tape from all the holes at the same time.
4. Observe the water flowing out through the side holes. This shows that water presses against the container's walls.

The conclusion is that liquids exert pressure in all directions. Water spurting from leaking pipe joints or holes can also be explained by the pressure exerted against the pipe walls.

A water-filled bottle has holes near its base. Water streams outwards through the side openings. The drawing labels the bottle, water, and holes.

See Fig. 6.7 in your NCERT textbook

Why is the base of a dam broad?

A dam is a structure used to hold back water. Stored water presses horizontally against its walls and vertically against its floor. Horizontal means sideways, while vertical means up or down. Water pressure near the bottom is very large because of the height of water above it.

A broad dam base helps support the structure and withstand this pressure. The explanation therefore combines two ideas: water pressure acts sideways, and it becomes greater with a greater height of water above the point considered.

What evidence shows that air exerts pressure?

The atmosphere is the envelope of air surrounding Earth. It extends many kilometres above the surface. Air contains nitrogen, oxygen, argon, carbon dioxide, and other gases in small quantities. Atmospheric pressure is the pressure exerted by the air around us.

How does a paper-plate activity reveal air pressure?

An inverted paper plate, meaning one turned upside down, has a stick attached so it can be lifted. It is placed on a flat surface and covered with chart paper. A central hole allows the stick to pass through the covering sheet.

Compare two identical chart-paper sheets, each about 70 cm × 56 cm. Fold one twice and leave the other unfolded. Lift the plate with each covering in turn. More effort is needed with the unfolded sheet, although the covering sheets have the same weight.

The unfolded sheet presents a larger area. Air exerts a greater force over that larger area, making lifting harder. This supports the conclusion that air exerts pressure. Air also presses against a balloon's walls, so an inflated balloon expands in all directions.

Why does a rubber sucker stick?

A rubber sucker is a flexible cup that can stick when pressed against a smooth, flat surface. Pressing pushes out most of the air between the cup and the surface, reducing the pressure inside. The surrounding air pressure is then higher.

This pressure difference holds the sucker against the surface. Pulling it away requires enough force to overcome the effect of that difference. The explanation depends on lower pressure inside, rather than on claiming that every bit of air has been removed.

Atmospheric pressure does not crush our bodies because pressure inside balances pressure outside. The internal pressure is associated with the movement of fluids and gases in tissues and organs.

The SI unit of air pressure is pascal (Pa). Air pressure may also be expressed in millibar, written mb, or hectopascal, written hPa; each equals 100 Pa.

Why does air move from one region to another?

Wind is moving air. Differences in air pressure cause air to move from a region of higher pressure to a region of lower pressure. Escaping air from an open inflated balloon or a punctured bicycle tube illustrates this movement.

What happens when two balloons are joined?

1. Take two similar thin-rubber balloons and a drinking straw. Secure one end of the straw inside an uninflated balloon.
2. Inflate the second balloon and hold its mouth closed so that air cannot escape.
3. Insert the free straw end into its neck and secure the connection, preventing air leakage during the connection.
4. Allow air to pass through the straw and observe how the sizes of the balloons change.

The pressure in the inflated balloon is higher, so some air moves into the uninflated balloon. Flow continues while that pressure difference exists. The balloons eventually become almost the same size, and airflow stops when their pressures become equal.

Note: Equal pressure is the condition that stops airflow in this activity. The balloon sizes are described as almost the same, not exactly identical. A larger pressure difference gives a higher speed of escaping air.

How does heating help create a pressure difference?

Warm air becomes lighter and rises. Its upward movement creates a lower-pressure region. Cooler air from surrounding higher-pressure areas moves into that region. This replacement connects heating of the ground with the movement of the air above it.

The pressure difference explains the direction of movement. The rising warm air and incoming cooler air are linked parts of the circulation, meaning the continuing movement of air through the system. This idea helps explain both everyday breezes and larger storms.

How do sea breezes and land breezes differ?

A sea breeze blows from sea towards land. A land breeze blows from land towards sea. Their directions are mainly explained by differences in air pressure over land and water, which develop as these surfaces heat differently.

What happens during the day?

Land heats faster than water during the day. Air above the land becomes warmer and lighter, so it rises. This creates a low-pressure region over the land. Air from the higher-pressure region over the sea moves towards it, producing a sea breeze.

What happens at night?

At night, the water is warmer than the land. A low-pressure region develops above the sea. Air then moves from the land towards the sea, producing a land breeze. In both cases, the wind moves towards the lower-pressure region.

To explain either breeze, identify the warmer surface first. Then connect warmer air with rising air, rising air with lower pressure, and the pressure difference with the direction of incoming air. This sequence explains the direction instead of merely naming it.

The words higher and lower pressure compare the two regions. They do not require a particular numerical pressure for either region. The key relationship is that air travels from the region of higher pressure into the region of lower pressure.

How can fast-moving air bring balloons together and lift roofs?

High-speed winds are accompanied by reduced air pressure. This relationship can produce movement that may seem surprising: blowing between suspended balloons makes them approach each other. The surrounding air pushes them towards the lower-pressure region between them.

What does blowing between balloons demonstrate?

1. Inflate two balloons to the same size and attach a string to each.
2. Hang them from a stick with a gap of 6 to 10 cm between them.
3. Blow into the narrow space between the balloons and observe their movement.
4. Blow harder and compare how quickly the balloons approach one another.

Moving air creates a lower-pressure region in the gap. Higher surrounding pressure pushes the balloons towards each other. Blowing harder makes them approach each other faster. The activity connects the movement with a pressure difference on the two sides of each balloon.

A person holds a horizontal stick supporting two inflated balloons on strings and blows into the gap between them. Both balloons hang close to the person's face.

See Fig. 6.13 in your NCERT textbook

Why may a weak roof blow away?

When high-speed wind passes over a house, pressure above the roof becomes lower than the pressure below it. If this pressure difference is large and the roof is weak, the roof may be blown away.

Keep both conditions in the explanation. Fast wind does not justify saying that every roof must lift. The effect depends on the pressure difference and the weakness of the roof. The balloon and roof examples both involve greater pressure acting towards a region of lower pressure.

How do storms develop into thunderstorms with lightning?

A storm involves strong winds accompanied by rain. A thunderstorm is a storm accompanied by lightning and thunder. Lightning is the bright flash produced by a sudden flow of electric charges, and thunder is the loud sound caused by rapid expansion of air heated by lightning.

How do clouds and rain develop?

When land heats, warm, moist air rises and produces a low-pressure area. Moist air contains water vapour, the gaseous form of water. Cooler surrounding air moves in, becomes heated, and rises in turn, maintaining wind circulation.

Rising air expands and cools. Its moisture undergoes condensation, the change of water vapour into liquid water, forming cloud droplets. These join into heavier drops; water returns as rain, hail, or snow. Hail consists of falling ice, while snow consists of ice crystals.

Storms are more frequent in hot, humid, tropical regions like India. Humid means containing substantial moisture; tropical refers to Earth's warm central belt. Under certain conditions, warm air rises to great heights where low temperatures turn water droplets into ice particles.

How are charges separated and discharged?

1. Strong upward and downward winds cause rubbing between ice particles and water droplets. Static electric charges, charges that build up on objects, develop within the clouds.
2. Lighter, positively charged ice particles move into the upper cloud. Heavier, negatively charged water droplets occupy the lower cloud. Positive and negative name the two opposite kinds of electric charge.
3. As the negatively charged lower cloud approaches the ground, the ground and nearby objects become positively charged.
4. Air normally acts as an electrical insulator, a material that resists the flow of charge. When charge build-up becomes very large, this insulating property breaks down.
5. Charges suddenly flow, producing lightning. Rapid heating makes the surrounding air expand and produce thunder.

Lightning can occur within a cloud, between clouds, or between a cloud and the ground. Moisture and strong winds are important requirements for thunderstorm formation. Their presence should not be turned into a claim that every storm becomes a cyclone.

How can lightning cause damage, and how do conductors protect buildings?

Lightning strikes can ignite fires and damage buildings. They can also cause severe burns or death in humans and animals. The powerful effects of lightning make protective measures important during thunderstorms, even though lightning can also occur between clouds without striking the ground.

What precautions reduce exposure?

Stay away from tall objects during lightning. Avoid an umbrella with a metallic rod, and get out of water. Do not lie flat on the ground. Inside a bus or car, a person is comparatively safer; this is not a claim of complete protection.

What is a lightning conductor?

A lightning conductor is a metal rod installed along a building to provide an easy path for electric charges to pass into the ground. A conductor is a material through which electric charges can move easily, unlike an insulator.

The rod has a pointed upper end that extends higher than the building's highest point. Its other end is buried deep in the ground. These features connect the upper part of the building with the ground through a conducting path.

The drawing shows a building with a pointed conductor extending above the roof. A conducting strip runs down the outside wall and connects to a part buried below ground.

See Fig. 6.18 in your NCERT textbook

The conductor protects the building by allowing charges to pass into the ground. Explaining it requires the complete path, including the buried end. Mentioning just a pointed rod above a roof leaves out the connection that makes charge transfer possible.

Air's normal insulating behaviour is also essential to understanding lightning itself. Charges can build up before a sudden discharge occurs. A discharge means a flow that releases accumulated electric charge. The conductor provides a path for that charge transfer at a building.

How do cyclones form, weaken, and affect coastal areas?

Cyclones are large storms that form over warm ocean water. They are spinning systems of clouds, winds, and rain surrounding a very low-pressure region. Their development combines warm water, rising moist air, released heat, incoming air, and Earth's rotation.

What maintains the spinning storm?

1. Ocean water heats, and warm, moist air above it rises.
2. Water vapour in the rising air condenses into raindrops. During evaporation, water takes in heat to become vapour; condensation releases that heat into the atmosphere.
3. The released heat warms the ascending air further, causing it to rise still higher and creating even lower pressure.
4. Air rushes in from surrounding regions and also rises. Earth's rotation, its spinning movement, causes the moving air to spin.
5. The repeated cycle produces high-speed winds revolving around a very low-pressure region, forming the cyclone.

The eye is the cyclone's central region of lowest pressure. Winds there are calm, while the surrounding region experiences strong winds and heavy rain. As a cyclone moves from ocean towards land, it generates higher wind speeds than regular thunderstorms. Once the cyclone reaches land, its source of moist air is cut off, and it gradually loses strength.

What damage can a cyclone cause?

Cyclone Amphan in 2020 had peak wind speeds of 270 kilometres per hour, written km/h. Strong cyclone winds push ocean water towards the shore. This surge, a rise and inward movement of seawater, can form a wall of water as high as 3 to 12 metres.

The water can flood coastal places and areas farther from the sea. Heavy rain may make rivers overflow and can trigger landslides, movements of earth down slopes. Seawater can contaminate drinking supplies and damage farmland; its salt can make soil less fertile.

Fallen trees and debris, scattered remains of damaged objects, may block roads and delay help. Power outages, interruptions to electricity supply, can last for days. A cyclone can leave damage requiring months or even years to repair, despite gradually weakening over land.

How do warnings and shelters help?

The India Meteorological Department (IMD) monitors cyclones and thunderstorms in India. Weather-monitoring satellites help track cyclones and predict their paths. Follow weather reports, alerts, and warnings. In cyclone-prone areas, keep an emergency kit with essential items ready and move quickly to a designated cyclone shelter during a cyclone.

Glossary

• Pressure — Force acting per unit area of a surface, considering forces perpendicular to that surface here.
• Pascal — The SI unit of pressure, equal to one newton per square metre.
• Water column — A vertical body of water whose height affects pressure at the point beneath it.
• Atmosphere — The envelope of air surrounding Earth and extending many kilometres above its surface.
• Atmospheric pressure — The pressure exerted by surrounding air on objects exposed to that air.
• Sea breeze — Wind moving from sea towards land as lower pressure develops over warmer land during daytime.
• Land breeze — Wind moving from land towards sea as lower pressure develops over the warmer sea at night.
• Condensation — The change of water vapour into liquid water, releasing heat into the surroundings.
• Lightning — A bright flash produced when a large build-up of electric charges causes sudden charge flow.
• Thunder — The loud sound produced by rapid expansion of air heated by lightning.
• Thunderstorm — A storm in which lightning and thunder accompany the strong winds and rain.
• Lightning conductor — A metal rod providing an easy path for electric charges to enter the ground from a building.
• Cyclone — A spinning system of clouds, high-speed winds, and rain formed over warm ocean water around very low pressure.
• Eye of a cyclone — The central region of lowest pressure where winds are calm despite strong surrounding winds and rainfall.

Common errors and misconceptions

• Misconception: A broad bag strap reduces the bag's weight. Correct: It spreads the same weight over a larger area, reducing pressure on the shoulders.
• Misconception: Pressure depends on force alone. Correct: Pressure is force divided by area; the contact area must also be considered.
• Misconception: A wider water pipe must produce greater bottom pressure at the same water height. Correct: Equal water-column heights produce equal balloon bulges in the pipe activity.
• Misconception: Liquids press only downwards. Correct: Liquids exert pressure in all directions, including against container walls.
• Misconception: A rubber sucker contains absolutely no air after pressing. Correct: Most of the air is pushed out, leaving lower pressure inside than outside.
• Misconception: Blowing between hanging balloons pushes them apart. Correct: Pressure falls between them, so greater surrounding pressure pushes them together.
• Misconception: Lightning must travel between a cloud and the ground. Correct: It can also occur within one cloud or between clouds.
• Misconception: The eye is the windiest part of a cyclone. Correct: Its winds are calm; strong winds and heavy rain occur in the surrounding region.

Exam-style questions with model answers

Q1. Two equally heavy bags have narrow and broad straps respectively. Which is more comfortable to carry, and why? [2 marks]

1. The bag with broad straps is more comfortable because its weight acts over a larger shoulder area.
2. For the same force, increasing the area reduces pressure, so the broad straps exert less pressure on the shoulders.

Q2. An elephant weighing 20000 N stands on four feet, each covering 0.25 m². Calculate the pressure on the ground, showing the total area and the formula. Here N means newton and m² means square metre. [3 marks]

1. The total contact area is the sum of the areas of all four feet: 4 × 0.25 m² = 1 m². The multiplication sign × combines the number of feet with each foot's area.
2. Pressure is perpendicular force divided by area. The elephant's weight supplies the force acting on the ground.
3. Pressure = 20000 N / 1 m² = 20000 N/m², or 20000 Pa, where Pa denotes pascal.

Q3. Two upright pipes of different widths contain water to equal heights and have similar rubber balloons attached at the bottom. Compare the bulges, explain the result, and predict what happens when the water height in one pipe increases. [3 marks]

1. The balloons initially bulge to the same extent. Equal water-column heights produce equal pressure despite the different weights of water in the two pipes.
2. This shows that the difference in the total weight of water does not determine the difference in bulging in this arrangement.
3. When the water height in one pipe increases, pressure at its bottom increases. Its balloon therefore bulges more than before.

Q4. Describe an activity using two similar thin-rubber balloons and a straw to demonstrate the direction of airflow between regions of different pressure. Include the final condition. [4 marks]

1. Secure one end of a straw inside an uninflated balloon. Inflate the other balloon and hold its mouth closed to retain air.
2. Insert the free straw end into the inflated balloon and secure it, preventing leakage. The balloons are now connected.
3. Some air moves from the inflated balloon, where pressure is higher, into the initially uninflated balloon, where pressure is lower.
4. Airflow stops when the pressures become equal. The balloons are then almost the same size, demonstrating movement from higher to lower pressure.

Q5. Two equally inflated balloons hang 6 to 10 cm apart, where cm means centimetre. Explain their movement when air is blown between them, the effect of blowing harder, and how the same pressure principle can affect a weak roof. [4 marks]

1. The moving air lowers the pressure in the gap between the balloons. High-speed air is accompanied by reduced pressure.
2. The higher air pressure on their outer sides pushes the balloons towards each other.
3. Blowing harder increases the speed at which the balloons approach each other.
4. Wind passing over a house can reduce pressure above its roof. If the pressure difference is large and the roof is weak, greater pressure below may cause the roof to blow away.

Q6. Explain how upward and downward winds in a cloud produce lightning and thunder. Include charge separation, the role of air, and the possible locations of lightning. [5 marks]

1. Strong upward and downward winds cause ice particles and water droplets to rub against one another. Static electric charges, meaning accumulated charges, develop within the clouds.
2. Lighter positively charged ice particles occupy the upper cloud, while heavier negatively charged droplets occupy its lower part. As the negatively charged lower cloud approaches the ground, the ground and nearby objects become positively charged.
3. Air normally acts as an electrical insulator, resisting charge flow. A very large build-up of charges breaks down this insulating property.
4. A sudden flow of charges produces the bright flash called lightning. This may occur within a cloud, between clouds, or between a cloud and the ground.
5. Lightning rapidly heats the surrounding air, causing expansion and the loud sound called thunder. A storm accompanied by lightning and thunder is a thunderstorm.

Q7. Explain how a cyclone forms over warm ocean water, identify its eye, and state why it gradually weakens after reaching land. [5 marks]

1. Warm ocean water heats the moist air above it. This air rises, and its water vapour condenses into raindrops as it rises.
2. Condensation, the conversion of vapour into liquid water, releases heat. This warms the rising air further, making it rise higher and creating still lower pressure.
3. Surrounding air rushes in and rises. Earth's rotation causes the moving air to spin, and the repeated cycle produces a rotating system of clouds, winds, and rain.
4. The eye is the central region of lowest pressure. Winds there are calm, although strong winds and heavy rainfall occur around it.
5. On reaching land, the cyclone loses its supply of moist air. It therefore gradually loses strength, even though it can still leave extensive damage behind.

Q8. Describe the construction of a lightning conductor and explain how it helps protect a building. [3 marks]

1. A lightning conductor is a metal rod installed along the building. Its pointed upper end extends above the highest point of the building.
2. The other end is buried deep in the ground, forming a continuous conducting connection from the upper part of the building to the ground.
3. The metal provides an easy path for electric charges to pass into the ground, helping protect the building from the effects of lightning.

Key takeaways

• Pressure is perpendicular force divided by area; spreading the same force over a larger area reduces pressure.
• Liquid pressure acts in all directions and increases at the bottom when the height of the liquid column increases.
• Atmospheric pressure acts on objects around us, while internal body pressure balances the pressure exerted from outside.
• Air moves from higher pressure to lower pressure; heating and rising warm air help establish these differences.
• Sea and land breezes have opposite directions because the relatively warmer surface differs between daytime and night.
• High-speed winds are accompanied by reduced pressure; weak roofs may lift when the pressure difference is large.
• Lightning follows a large build-up of electric charges, and the rapid expansion of heated air produces thunder.
• Cyclones develop over warm ocean water, have calm central eyes, and gradually weaken when their moist-air supply is cut off over land.

Test yourself

Why does a sharp knife cut an apple more easily than a blunt edge?

The sharp edge presents a smaller area, producing greater pressure for the same applied force.

What is another name for one newton per square metre?

It is one pascal, the SI unit used to express pressure.

What happens to a bottom balloon when the water column above it becomes taller?

The pressure at the bottom increases, making the attached balloon bulge more.

Does a rubber sucker stick because every bit of air has been removed?

No. Most air is pushed out, reducing internal pressure below the surrounding air pressure.

When does airflow stop between the connected balloons?

It stops when their air pressures become equal; their sizes are then almost the same.

Why does a sea breeze blow towards land during the day?

Land heats faster, so air above it warms and rises. Air moves from higher pressure over the sea towards lower pressure over land.

Is the eye of a cyclone a region of strong winds?

No. Winds at the eye are calm, while the surrounding region experiences strong winds and heavy rainfall.

Why does a cyclone gradually weaken over land?

Its supply of moist air is cut off after reaching land, so it gradually loses strength.