Pressure, Pressure Everywhere. How much does it weigh?

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Do you know that the air in an average sized room weighs about 50 kg?

Air puts the pressure from all sides, you get the air pressure of the weight equivalent of a small car on your body always!

This is because we are surrounded by air, we call it it our atmosphere. Earth's atmosphere is about 480 kilometers thick, but most of it is within 16 km the surface, it thins out as we move up. The weight of gases in our atmosphere creates the pressure. Air pressure decreases with altitude. At sea level, air pressure is about 1 kilogram per square centimetre  At 10,000 feet (3 km), the air pressure is reduced to 0.7 kg per square cm.

An interesting thing happens when the air pressure changes – things start to move. The cloud move, the wind starts and so on. This difference in pressure that causes movement is what creates winds and tornadoes.
Here are some of the experiments we can do to learn more about pressure.


Water Glass Magic Trick
  1. Take a small size glass of width less than a playing card.
  2. Fill this glass one-third with water. 
  3. Cover the glass with the playing card card and invert (holding the card in place). 
  4. Remove your hand from the card. 
Magic! The card stays in place.

The card experiences about 7 kg of force pushing upward by the air and only about 300g of force pushing downward from the water – hence the card stays in place.

Egg Magic Trick

  1. Take a hard boiled egg and remove the shell
  2. Use a large neck glass mil bottle with a neck large enough that the egg can be squeezed through.
  3. Light some new paper and toss it inside the bottle.
  4. While the paper is burning,  quickly place the egg (small-end down) on the mouth of the bottle. 
Magic! The Egg falls inside.

When you burnt the paper, the air inside gets used up by the flame, lowering the air pressure inside the bottle. The outside higher pressure pushes on the egg and pops it in.


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