Class 8 Science Pressure, Winds, Storms, and Cyclones
Class 8 Science Pressure, Winds, Storms, and Cyclones
1. Introduction
Pressure is the force applied per unit area. It is an important concept in understanding weather phenomena, wind formation, and storms. Changes in air pressure cause winds, storms, and cyclones.
2. Pressure
Definition: Pressure = Force / Area
Unit: Pascal (Pa) or N/m²
Examples of pressure:
Knife cuts easily due to small area → high pressure
Snowshoes prevent sinking → reduce pressure
Liquids and Pressure:
Pressure in a liquid acts equally in all directions.
Depends on height of liquid column and density of liquid.
Atmospheric Pressure:
Pressure exerted by the air around us.
Measured using a barometer.
Decreases with height above sea level.
3. Winds
Winds are air moving from high-pressure areas to low-pressure areas.
Causes: Unequal heating of Earth’s surface → differences in pressure.
Local Winds:
Land breeze → night (land cools faster)
Sea breeze → day (land heats faster)
Global Winds: Result from unequal heating on large scale and Coriolis effect.
4. Storms
Definition: Strong winds caused by rapid fall in atmospheric pressure.
Can cause damage to property and crops.
Types: Thunderstorms, Dust storms, Hailstorms
Thunderstorms:
Accompanied by lightning and thunder
Usually occur in hot, humid conditions
Dust Storms:
Strong winds carrying sand/dust
Common in deserts
5. Cyclones
Definition: Cyclones are large, rotating storms with low-pressure centers.
Characteristics:
Very strong winds
Heavy rainfall
Rotate clockwise in southern hemisphere and counterclockwise in northern hemisphere
Types of Cyclones:
Tropical cyclones → oceans, high humidity, warm temperatures
Extra-tropical cyclones → in temperate regions
Cyclone Safety Measures:
Evacuate low-lying areas
Stay indoors away from windows
Follow government alerts and warnings
6. Key Terms
Term
Meaning
Pressure
Force per unit area
Atmospheric Pressure
Pressure exerted by the air around us
Wind
Movement of air from high to low pressure
Storm
Strong winds due to rapid pressure drop
Cyclone
Large, rotating storm with low-pressure center
Barometer
Instrument to measure atmospheric pressure
Land Breeze
Air flow from land to sea at night
Sea Breeze
Air flow from sea to land during day
7. Examples of Pressure in Daily Life
Knife → cuts easily due to small surface area
High heels → higher pressure on floor
Snowshoes → reduce pressure on snow
Blood pressure → force of blood on artery walls
8. Possible Questions
Very Short Answer Questions (1–2 marks)
Define pressure.
What is atmospheric pressure?
Name two types of local winds.
What instrument measures atmospheric pressure?
Define cyclone.
Short Answer Questions (3–5 marks)
Explain how pressure in liquids works.
Describe land and sea breezes.
List two types of storms.
How do cyclones form?
Long Answer Questions (6–8 marks)
Explain the relation between pressure differences and wind formation.
Describe the types and characteristics of cyclones.
Explain atmospheric pressure and its variation with height.
Discuss measures to stay safe during storms and cyclones.
Multiple Choice Questions (MCQs)
Pressure = _______ a) Force × Area b) Force / Area c) Area / Force d) Force + Area Answer: b
Winds blow from: a) Low to high pressure b) High to low pressure c) Equator to poles only d) North to South only Answer: b
Barometer measures: a) Temperature b) Wind speed c) Atmospheric pressure d) Humidity Answer: c
Fill in the Blanks
Pressure = _______ / _______
Sea breeze occurs during the _______.
Cyclones rotate _______ in northern hemisphere.
True/False Questions
Atmospheric pressure increases with height. False
Land breeze occurs at night. True
Winds are caused by differences in pressure. True
Match the Following
Column A
Column B
Barometer
Measures atmospheric pressure
Land breeze
Night, land to sea
Sea breeze
Day, sea to land
Cyclone
Low-pressure rotating storm
Dust storm
Strong winds carrying dust
Pressure Basics
Pressure is defined as: a) Force × Area b) Force / Area c) Area / Force d) Force + Area Answer: b
Unit of pressure is: a) Newton b) Pascal c) Joule d) Watt Answer: b
Pressure depends on: a) Force and area b) Mass only c) Volume only d) Temperature only Answer: a
Knife cuts easily because: a) Large area → high pressure b) Small area → high pressure c) Small area → low pressure d) Large area → low pressure Answer: b
Snowshoes prevent sinking because they: a) Reduce force b) Increase pressure c) Increase area → reduce pressure d) None of these Answer: c
Pressure in liquids acts: a) Only downward b) Equally in all directions c) Horizontally only d) Randomly Answer: b
Atmospheric pressure is measured using: a) Thermometer b) Barometer c) Hygrometer d) Anemometer Answer: b
Atmospheric pressure: a) Increases with height b) Decreases with height c) Remains constant d) Depends on weight only Answer: b
Higher atmospheric pressure is found: a) At mountaintops b) At sea level c) In space d) At poles only Answer: b
Low-pressure area generally causes: a) Calm weather b) Storms and winds c) High pressure d) No wind Answer: b
Winds
Winds blow from: a) High to low pressure b) Low to high pressure c) Equator to poles only d) North to South always Answer: a
Land breeze occurs: a) During the day b) At night c) Only in summer d) Only in winter Answer: b
Sea breeze occurs: a) During the day b) At night c) Only in summer d) Only in winter Answer: a
Sea breeze is caused by: a) Land heating faster than sea b) Sea heating faster than land c) Unequal pressure d) Both a and c Answer: d
Local winds include: a) Land and sea breezes b) Cyclones c) Trade winds d) Westerlies Answer: a
Global winds result from: a) Unequal heating of Earth b) Ocean currents only c) Local heating d) Mountains Answer: a
Wind speed is measured using: a) Barometer b) Thermometer c) Anemometer d) Hygrometer Answer: c
Winds are important because they: a) Distribute heat and moisture b) Cause cyclones c) Increase pollution d) Only blow dust Answer: a
Sea breeze is: a) Cold air from land to sea b) Cold air from sea to land c) Warm air from sea d) Hot air from land Answer: b
Land breeze is: a) Nighttime airflow from land to sea b) Daytime airflow from land to sea c) Nighttime airflow from sea to land d) Daytime airflow from sea to land Answer: a
Storms
Storms are caused by: a) High pressure b) Rapid fall in atmospheric pressure c) Equal pressure d) Friction Answer: b
Thunderstorms are accompanied by: a) Lightning and thunder b) Only wind c) Only rain d) Fog Answer: a
Dust storms are common in: a) Deserts b) Mountains c) Oceans d) Plains Answer: a
Hailstorms occur due to: a) Friction b) Strong upward air currents and freezing of water c) Low humidity d) Earthquakes Answer: b
Storms can cause: a) Crop damage b) Property loss c) Injuries d) All of the above Answer: d
Thunder is caused by: a) Lightning heating air → rapid expansion b) Wind speed c) Rainfall d) Pressure alone Answer: a
Lightning is: a) Flow of electric charge in clouds b) Air movement c) Water vapor d) Magnetic effect Answer: a
Storms are measured by: a) Barometer b) Anemometer c) Hygrometer d) Thermometer Answer: b
Cyclones are stronger than normal storms because: a) Low pressure + rotation + strong winds b) High pressure only c) Friction d) Temperature alone Answer: a
Hailstones are formed in: a) Hot air only b) Cold upper clouds c) Sea water d) Dusty plains Answer: b
Cyclones
Cyclones are: a) Small whirlwinds b) Large, rotating storms with low-pressure center c) Local winds d) Dust storms only Answer: b
Tropical cyclones form over: a) Oceans near equator b) Mountains c) Deserts d) Ice caps Answer: a
Cyclones rotate clockwise in: a) Northern hemisphere b) Southern hemisphere c) Both hemispheres d) Equator Answer: b
Cyclones rotate counterclockwise in: a) Northern hemisphere b) Southern hemisphere c) Equator d) Both hemispheres Answer: a
Cyclones bring: a) Strong winds b) Heavy rainfall c) Flooding d) All of the above Answer: d
Extra-tropical cyclones occur in: a) Temperate regions b) Tropical oceans c) Deserts d) Polar regions only Answer: a
Evacuation is important during cyclones because: a) Prevent injuries b) Protect property c) Avoid floods d) All of the above Answer: d
Cyclone warnings are issued by: a) Meteorological department b) Police c) School teachers d) Farmers Answer: a
Cyclones are formed due to: a) Unequal heating of water surface + low pressure + Coriolis effect b) Earthquakes c) Mountain winds d) Dust storms Answer: a
Eye of the cyclone is: a) Region of calm at center b) Strongest wind region c) Rainfall zone d) Low pressure zone only Answer: a
True/False
Atmospheric pressure decreases with height. True
Winds blow from low to high pressure. False
Land breeze occurs during night. True
Cyclones are low-pressure rotating storms. True
Hailstones are formed in hot air near ground. False
Fill in the Blanks
Pressure = _______ / _______ Answer: Force / Area
Winds blow from _______ to _______ pressure. Answer: High, Low
Sea breeze occurs during the _______. Answer: Day
Cyclones rotate _______ in northern hemisphere. Answer: Counterclockwise
Atmospheric pressure is measured by a _______. Answer: Barometer