The same force spread over a small area presses much harder. That single idea explains sharp knives, wide tyres — and the winds that circle the planet.
Pressure is force divided by area. Same force, smaller area, far greater pressure.
📌 Pressure = force ÷ area
A sharp knife cuts better because its thin edge has a tiny area, so the pressure is huge.
Wide tyres and camel feet spread the same weight over a large area, so they do not sink.
A school bag with broad straps hurts less than one with thin cords — same load, more area.
Liquid pressure increases with depth and pushes in all directions, not just downwards. That is why a dam is built much thicker at the bottom than at the top.
Air has weight, and the column of air above you presses down all the time — you simply do not notice it because it presses from every side equally.
🎈 Air pressure at work
| What happens | Why |
|---|---|
| A sucker sticks to a wall | air is pushed out, so outside air presses it on |
| A straw draws up a drink | you lower the pressure inside, and outside air pushes the liquid up |
| Ears pop in the hills | air pressure falls as you climb |
| A balloon bursts when squeezed | the air inside is forced into a smaller space |
A straw does not "pull" the drink. You reduce the pressure inside the straw, and the atmosphere outside pushes the liquid up. This is a classic exam question, and "sucking" is the wrong explanation.
Wind is simply air moving from high pressure to low pressure. Heat is what creates the difference.
🌀 How wind is made
The sun heats the ground unevenly. Warm air expands, becomes lighter and rises.
That leaves a region of low pressure behind.
Cooler, denser air rushes in to fill it — and that moving air is wind.
🌀 The names
| Name | What it is |
|---|---|
| Land and sea breeze | daily wind at a coast; by day it blows from the sea to the land |
| Monsoon | seasonal wind; in summer it blows from the sea, bringing rain to India |
| Thunderstorm | rising warm moist air building tall clouds, with lightning and thunder |
| Cyclone | a huge spinning system of very low pressure over a warm sea |
| Tornado | a narrow, violent, fast-spinning funnel of air |
Why the monsoon reverses. In summer the land heats faster than the sea, so air rises over the land and moist sea air rushes in — bringing rain. In winter it is the other way round, and the wind blows from the land, which is why it is dry.
12 questions on pressure, winds and cyclones. 🍀