Final answer:
Air pressure is the force exerted by the weight of air molecules in the Earth's atmosphere. Its value decreases with altitude due to the decrease in air molecules. A balloon and a straw can be used as examples to understand air pressure.
Step-by-step explanation:
Air Pressure
Air pressure is the force exerted by the weight of air molecules in the Earth's atmosphere. It is the result of the constant collisions between air molecules and the surfaces they come in contact with. The pressure decreases as you move higher up in the atmosphere due to the decrease in the number of air molecules.
One way to understand air pressure is by imagining a balloon. When you blow air into a balloon, the air molecules inside push against the walls of the balloon, creating a greater pressure inside compared to the outside. This is why the balloon expands. Similarly, in the Earth's atmosphere, the air molecules are constantly colliding with each other and the surface, creating pressure.
Examples:
- When you suck on a straw, you reduce the pressure inside the straw, causing the higher atmospheric pressure outside to push the liquid up the straw.
- The barometer uses air pressure to measure weather changes. A rise in air pressure indicates fair weather, while a decrease indicates a possible storm.
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