Track quiz
Here are the ten rules, in the exact words each lab uses.
| Idea | The rule, as the lab applies it |
|---|---|
| Force over area | Pressure is force divided by area. Its unit is the pascal (Pa), one newton on one square metre. The same force on a smaller area gives a higher pressure. |
| Liquids press too | A liquid presses on the bottom and on the sides. For the same liquid, the taller the column, the higher the pressure. The width of the vessel makes no difference. |
| The air presses | Air is a layer around the Earth called the atmosphere. It has weight, so it presses on everything, in every direction. This is atmospheric pressure. |
| Why nobody feels it | Air presses on every side of you. The pressure inside your body is equal to it. Equal pressures on both sides balance, so nothing crushes you. |
| High to low | Air moves from high pressure to low pressure. This moving air is wind. It stops when the two pressures are equal. |
| Where a wind gets started | Warm air is lighter, so it rises. This leaves an area of low pressure. Cooler air from a high pressure area moves in. This moving air is wind. |
| A breeze that turns around | By day, land is warmer. Wind blows from the sea to the land. This is a sea breeze. By night, the sea is warmer. Wind blows from the land to the sea. This is a land breeze. |
| How a cyclone grows | Warm moist air over the sea rises. Its vapour condenses and gives out heat, so the air rises more. The pressure falls, and air rushes in. The Earth spins the air. This is a cyclone. |
| Fast air | Fast-moving air has lower pressure than still air beside it. The higher pressure pushes things towards the fast air. |
| Lightning | Lightning is a sudden flow of charge. It heats the air, and the hot air makes thunder. |
A force of 100 N acts on an area of 4 m². What is the pressure?
A bag has thin straps. Another bag of the same weight has wide straps. Which hurts more?
A wide plank is laid on soft mud. A person stands on it. Why do they sink less than on bare mud?
Two pipes hold water to the same height. One is narrow. One is wide. Balloons are tied at the bottom. Which bulges more?
You want more water pressure at a tap. Where should the tank go?
Holes are made low on the side of a full bottle. What comes out?
Why does air press on things?
Air presses on you with a huge force. Why are you not crushed?
A rubber sucker is pressed on a smooth tile. Why does it stick?
Two balloons are joined by a straw. One is full. One is flat. Which way does the air go?
When does the air between two balloons stop moving?
A road warms in the Sun. Which way does the wind blow near the ground?
It is a hot afternoon on a coast. Which way does the wind blow?
Where is the wind calm in a cyclone?
Wind blows fast over a roof. Which air has the higher pressure?
After a flash, air makes a loud sound. What made the sound?
Chapter 6 of your NCERT book is Pressure, Winds, Storms, and Cyclones. Read it next. Use pressure = force ÷ area when you meet its sums.
Next: Particulate Nature of Matter. It asks what the thin air is made of.