Pressure, Winds, Storms and Cyclones Class 8

Quick answer

Pressure is force per unit area (P=F/A), measured in pascals. Liquids and gases exert pressure, pressure differences drive winds, and atmospheric convection produces storms. Warm oceans and rotation support cyclones. All 13 NCERT exercises are addressed.

Key points

Pressure equals perpendicular force divided by area.
Smaller contact area means greater pressure for the same force.
Liquid pressure increases with depth and acts on vessel walls.
Atmospheric pressure acts in all directions.
Air pressure differences drive winds.
Thunderstorms form through strong convection and charge separation.
Cyclones are rotating low-pressure systems fed by warm oceans.
Follow IMD alerts and seek safe shelter during storms.

Use these notes alongside your current textbook. Check important formulas, worked answers and syllabus coverage with your teacher or official learning material.

Pressure, Winds, Storms, and Cyclones — NCERT Class 8 Science Chapter 6

Direct answer: Pressure is perpendicular force per unit area (P=F/A), measured in pascals. Liquids and gases exert pressure; pressure differences drive winds. Strong convection can create thunderstorms, and warm oceans support tropical cyclones.

Why do broad bag straps feel more comfortable? Why are water tanks mounted high? What makes a cyclone rotate? These everyday questions link forces, air pressure and weather.

Textbook: NCERT Curiosity Reprint 2026–27, Chapter 6, pages 80–97. The guide covers all six sections, six numbered activities and all 13 numbered exercise questions, with original practice clearly distinguished.

6.1 Pressure

Pressure is perpendicular force per unit area: P=F/A. SI unit pascal (Pa)=N/m². A force of 100 N over 2 m² creates 50 Pa. Broad bag straps reduce pressure; sharp knives concentrate it. Liquid pressure increases with depth and acts sideways as well as downwards. At a fixed depth in the same liquid, pressure does not depend on vessel width. Overhead tanks supply pressure through vertical height difference.

6.2 Pressure Exerted by Air

Air exerts atmospheric pressure in all directions. A suction cup adheres because pressure inside it is lower than outside. Pressure differences, not suction as a mysterious force, explain its grip. The body is not crushed because internal and external pressures approximately balance. 1 millibar=1 hectopascal=100 Pa.

6.3 Formation of Wind

Pressure gradients cause air to accelerate. During daytime, land generally warms faster than sea, and sea breeze flows toward land. At night land breeze may flow toward the sea. Earth's rotation and friction affect real wind directions.

6.4 High-Speed Winds and Pressure

Blowing between hanging balloons can lower pressure between them and make them approach. Fast winds can damage roofs through pressure differences and structural loading. Safety correction: do not open windows during storms to equalise pressure; secure doors and windows and follow local emergency guidance.

6.5 Storms, Thunderstorms, and Lightning

Warm moist air rises, cools and condenses. Strong convection produces rain, gusts and thunderstorms. Collisions among ice and water particles help separate electric charges. A lightning discharge heats air rapidly, producing thunder. Shelter in a substantial building or fully enclosed hard-top car; avoid open areas, trees, water, windows and plumbing. Outdoor crouching is not a safe substitute for shelter.

6.6 Cyclone

Over warm oceans, moist rising air condenses and releases latent heat, helping sustain low pressure and powerful rotating winds. Earth's rotation contributes to circulation. The eye may be relatively calm but the eyewall is dangerous. Cyclones cause storm surge, flooding, wind damage and power outages. Follow IMD warnings and evacuate to designated shelters when instructed.

Activities and diagrams

Table 6.1 compares sharp/blunt edges and pointed nails. Activities 6.1–6.2 show liquid pressure with balloons and bottle holes; 6.3–6.4 demonstrate atmospheric pressure with paper and a suction cup; 6.5 connects inflated and uninflated balloons; 6.6 blows between suspended balloons. Use teacher-supervised setups; do not use heated needles or sharp tools independently. Figures 6.21–6.25 are required for exact vessel and coastal-tree labelling.

Formula and concept table

Concept	Formula or explanation	Example
Pressure	P=F/A	200 N / 2 m² =100 Pa
Liquid pressure	Increases with depth	Lower taps often stronger
Atmospheric pressure	Air pushes on surfaces	Suction cup
Wind	Pressure gradient	Sea breeze
Thunderstorm	Convection and electric discharge	Lightning and thunder
Cyclone	Rotating ocean-fed low pressure	Eye and eyewall

Keep the Curiosity Alive — textbook questions and solutions

Question 1(i). In three connected open vessels P, Q and R (Fig. 6.21), what will the settled water levels be?

Step-by-step explanation: Connected liquid surfaces settle to equal heights under equal atmospheric pressure.

Final answer: Option (d), equal levels.

Question 1(ii). Which rubber sucker sticks better: M on smooth surface or N on rough surface?

Step-by-step explanation: Smooth surfaces seal better, retaining the pressure difference.

Final answer: Option (c), M only.

Question 1(iii). How can ground-floor water pressure from a rooftop tank be increased?

Step-by-step explanation: Increase the vertical water-level difference.

Final answer: Option (a), raise the tank.

Question 1(iv). Two vessels A and B have the same water depth but different bottom areas (Fig. 6.22). Compare pressure and bottom force.

Step-by-step explanation: Pressure is equal at equal depth. Bottom force equals pressure times base area; the larger base receives greater force.

Final answer: P_A=P_B; larger-area base has greater force. Confirm option letter from original figure.

Question 2(i). True or false: Air flows from high-pressure to low-pressure regions.

Step-by-step explanation: Pressure differences drive airflow.

Final answer: True.

Question 2(ii). True or false: Water pushes only on the bottom of its container.

Step-by-step explanation: Water also pushes sideways on walls.

Final answer: False.

Question 2(iii). True or false: The eye of a cyclone is the stormiest region.

Step-by-step explanation: The eye is relatively calm; the eyewall is dangerous.

Final answer: False.

Question 2(iv). True or false: A car is safer than an open field during lightning.

Step-by-step explanation: A fully enclosed hard-top vehicle offers meaningful protection.

Final answer: True for an enclosed hard-top vehicle.

Question 3. Why does a boy standing on sand sink deeper than when lying on it?

Step-by-step explanation: Standing concentrates the same weight on the smaller area of the feet, increasing P=F/A.

Final answer: Standing causes greater pressure.

Question 4. An elephant weighs 20,000 N and stands on four feet, each 0.25 m². Find pressure.

Step-by-step explanation: Total contact area=4×0.25=1 m²; pressure=20,000/1.

Final answer: 20,000 Pa.

Question 5. Boat A has five 700 N passengers and base 7 m². Boat B has three 700 N passengers and base 3.5 m². Which passenger load gives greater pressure?

Step-by-step explanation: A: 3500/7=500 Pa. B: 2100/3.5=600 Pa. Difference=100 Pa. Boat weights are not included.

Final answer: Boat B by 100 Pa.

Question 6. Would lightning form in the same way if air were a good electrical conductor?

Step-by-step explanation: Charges would leak and redistribute before a large insulating-air breakdown accumulated.

Final answer: No, sudden lightning discharge would be less likely.

Question 7. Two balloons cover holes at different depths on a water bottle (Fig. 6.24). Will both bulge equally?

Step-by-step explanation: Water pressure acts sideways and increases with depth.

Final answer: Both bulge; the lower balloon bulges more.

Question 8. Explain how a storm becomes a cyclone.

Step-by-step explanation: Warm ocean water supplies vapour; rising moist air condenses and releases heat; low pressure intensifies and rotation organises the winds.

Final answer: A rotating, ocean-fed low-pressure storm develops.

Question 9. Which side A or B in Fig. 6.25 is land during a summer-afternoon sea breeze?

Step-by-step explanation: Sea breeze blows from sea toward land, so trees lean toward land. Check the figure to assign its A/B letter.

Final answer: Land lies in the downwind direction; exact letter needs the figure.

Question 10. Describe an activity showing airflow from higher to lower pressure.

Step-by-step explanation: Join an inflated and uninflated balloon using a sealed straw; allow air to flow between them.

Final answer: Air passes from the inflated balloon toward the other until pressures approach balance.

Question 11. What is a thunderstorm and how does it form?

Step-by-step explanation: Warm moist air rises, cools and condenses; vigorous convection, precipitation and electric charge separation lead to lightning and thunder.

Final answer: A convective storm accompanied by lightning and thunder.

Question 12. How is lightning produced?

Step-by-step explanation: Storm-cloud particle collisions separate charges; a strong electric field breaks down air and creates a sudden discharge.

Final answer: A rapid electric discharge produces lightning.

Question 13. Why do large banners have holes?

Step-by-step explanation: Openings allow some wind through and reduce the wind force on the banner.

Final answer: To reduce wind loading.

Additional original practice

Question Original 1. Find pressure when 120 N acts on 0.03 m².

Step-by-step solution: 120÷0.03=4000.

Final answer: 4000 Pa.

Question Original 2. Convert 1015 hPa into pascals.

Step-by-step solution: Multiply 1015 by 100.

Final answer: 101,500 Pa.

Question Original 3. Why should windows not be opened during a cyclone?

Step-by-step solution: Flying debris, wind pressure and rain make openings hazardous; official shelter guidance prioritises secure openings.

Final answer: Keep doors and windows closed and secured.

Question Original 4. Why is the eyewall dangerous when the eye is calm?

Step-by-step solution: The eyewall contains intense winds and thunderstorms surrounding the central eye.

Final answer: The eyewall is a region of severe weather.

Revision, HOTS and safety

MCQ: Which unit measures pressure: N, Pa or kg? Answer: Pa. HOTS: A wide snowshoe spreads the same weight over a greater area, reducing pressure. Safety: Seek proper lightning shelter, secure doors and windows during severe winds, and follow IMD and local authority evacuation instructions.

Source and verification limits

Official NCERT Chapter 6 PDF. Exercise wording is paraphrased. For Questions 1(iv) and 9, exact figure-dependent option letters are not guessed; consult the original labelled figures. The textbook suggestion to open windows during storms must not override current emergency safety guidance.