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.
Study Zone is free for our students — you just need to log in with your WhatsApp number first.
Log in with WhatsApp →The first two chapters of every book are free once you're logged in. To open this one, request an unlock and we'll get back to you on WhatsApp.
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. 🍀
