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ATMOSPHERE
Lesson 2 - Page 6

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If you blow over a piece of paper, it actually lifts up. This is caused when air flows over a surface and its speed increases and its pressure decreases. This is the Bernoulliís Principle and it explains how an aircraft wind can generate a lifting force, just like in the piece of paper. Daniel Bernoulli in the 1700's first developed different aerodynamic principles that helped explain not only planes but why roofs can just lift off a house during a hurricane.

By blowing hard and steady, you can demonstrate a version of Bernoulliís Principle. With a piece of straw and ping pong ball, you can demonstrate magical "floating. You need to shoot a stream of air directly up, as in the diagram. You can use a hair dryer if you are doing this at home. The air is in rapid motion. Its pressure is lowered. The floating ball is actually kept in place by the column of upward rushing air. If it wobbles, the "jet stream" on either side, forces the ball back to its optical illusion.

There are many tricks that you can perform with air. These exercises are meant to open your eyes to explain the mysterious "ghosts" that open and close doors in your house.


Daniel Bernoulli


   

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