Showing Revision 1 created 11/04/2012 by podsinprint_user1.

1. Title:
   10x-05 Under Pressure
2. Description:

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   So, what are the consequences of something
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   being placed under pressure? Well, if I look
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   at this balloon, I can apply pressure to it by
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   exerting a force over its area. And when I do,
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   well, the balloon actually gets a little bit
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   smaller. The air inside the balloon gets a
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   little more densely packed together. And
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    in fact, this is exactly what happens on earth.
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    Out here, far away from the surface of the
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    earth, there are not very many air molecules.
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    This is a low pressure environment and
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    with nothing to weigh down on these air
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    molecules from above, they’re basically
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    free to play. They are free to move around.
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    Now below this outer layer of the
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    atmosphere, where all these air molecules
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    are sort of weighing on the atoms below it,
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    the molecules below it, and so these become
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    a little more densely packed. And as we go
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    even further down towards the surface of
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    the earth, where us humans tend to live,
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    the air gets even more densely packed.
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    And so we see that down near the surface
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    of the earth, where we have high pressure,
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    we also have a high density of air molecules.
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    And this high density of air molecules makes
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    us humans living at the surface very happy.
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    So I want to know, why do humans like high
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    pressure so much? Maybe the weight from
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    all that air above us keeps us from growing
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    too tall. Maybe air pollution tends to go to
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    regions of low pressure. Or maybe it means
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    that there’s lots of oxygen for us to breathe.
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    Go ahead and choose the best answer.