NCERT Curiosity · Class 8 · Science
Pressure, Winds, Storms, and Cyclones
Two identical bags, same weight — narrow straps hurt, broad straps don't. The same force spread differently feels completely different.
Pressure Wind Thunderstorms Cyclones
Key idea
Pressure = Force ÷ Area
A force of 100 N over 2 m² gives a pressure of 50 N/m². The SI unit of pressure is the pascal (Pa).
Key idea
Liquids Exert Pressure
Height matters

Taller liquid columns press harder at the bottom — that's why tanks sit high, to boost tap pressure.

A dam's shape

Built broader at the base than the top, since water pressure is greatest near the bottom.

Key idea
We aren't crushed by the atmosphere because our own pressure balances it.
A rubber sucker sticks the same way — pushing air out from beneath it lowers the pressure inside.
Key idea
How Wind Forms
High to low pressure

Air always moves from high pressure to low pressure — a bigger difference means faster wind.

Sea and land breeze

Sea breeze by day, when land heats faster; land breeze by night, when land cools faster.

Key idea
Fast wind creates lower pressure above it.
If a storm's pressure difference is large enough, a weak roof can blow off — keeping doors and windows open reduces that difference.
Key idea
How a Thunderstorm Forms
Warm air rises
→
Clouds & rain form
→
Winds separate charge
→
Charge discharges
Key idea
Lightning Safety
During a storm

Stay away from tall objects, crouch low, avoid metal umbrellas and water. A car is comparatively safe.

Lightning conductor

A pointed rod, connected to the ground, gives lightning a safe path to discharge.

Key idea
How a Cyclone Forms
Rising warm air

Over warm ocean water, rising air lowers pressure further; Earth's rotation adds the spin.

The eye

A calm, lowest-pressure centre, surrounded by the strongest winds and heaviest rain.

Key idea
Cyclone Effects, and Watching the Sky

Destruction

Storm surges, flooding, and power outages — cyclones weaken once over land.

Tracking and warning

The IMD and satellites predict cyclone paths, reducing their impact.

Chapter · key terms to remember
Key Terms

Pressure

Force per unit area; SI unit N/m² (pascal).

Atmospheric pressure

The pressure exerted by air around us.

Wind

Air moving from high to low pressure.

Chapter · key terms to remember
More Key Terms

Sea breeze / Land breeze

Sea-to-land wind by day / land-to-sea by night.

Thunderstorm

A storm with lightning and thunder.

Lightning conductor

A rod giving lightning a safe path to ground.

Chapter · key terms to remember
More Key Terms

Cyclone

A spinning storm system over warm ocean water.

Eye of the cyclone

The calm, lowest-pressure centre.

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