Pressure Exerted by Liquids
Liquids and gases are collectively called fluids. Unlike solids, fluids exert pressure in all directions (downwards, sideways, and upwards).
Key Properties of Liquid Pressure:
- Pressure increases with Depth:
- The deeper you go, the more weight of water is above you.
- Activity: If you attach a balloon to the bottom of a pipe and fill it with water, the balloon bulges. If you fill it higher (more depth), the balloon bulges more.
- Liquids exert pressure on walls:
- Activity: A plastic bottle with holes at the bottom will shoot water out. This proves water pushes sideways against the container walls.
- Pressure is equal at the same depth:
- If you make holes at the same height all around a bottle, water spurts out the same distance from all holes.
Why are Dam walls thicker at the bottom?
Because water pressure is highest at the bottom of the reservoir. A thick base is needed to withstand this immense horizontal pressure.
Atmospheric Pressure
We live at the bottom of a huge ocean of air called the Atmosphere. Air has weight, and this weight exerts pressure on us.
- Atmospheric Pressure: The pressure exerted by the air around us.
- Magnitude: On an area of (roughly the size of your head), the force of air is nearly 2250 N (equal to a mass of 225 kg).
Why don’t we get crushed?
Because the pressure inside our bodies (blood pressure, dissolved gases) is roughly equal to the atmospheric pressure outside. They balance each other out.
The Rubber Sucker Experiment
When you press a rubber sucker against a wall, you force the air out from between the cup and the wall.
- Inside: Vacuum (Low pressure).
- Outside: Atmospheric air (High pressure).
- Result: The atmosphere pushes the sucker firmly against the wall, making it stick.