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[tony.podrasky]

GN OMs;

In Junior High School science, the teacher demonstrated how
sound travels through air - and how it doesn't through a vacuum.

He took an electric doorbell and put it on a rubber platform
and placed a bell jar over it. You could hear it ringing. Then
he turned on a vacuum pump and drew out all the air in the
bell jar. As the pressure went negative, the bell was less and
less audible. Pretty soon you could barely perceive it.

Then the teacher stopped the pump and opened a vent on the side
of the bell jar and as you heard the hissing, you could hear the
bell get louder.

When the experiment was done, he asked the class:"what happened
when I started the vacuum pump?".

The smart little girl said: "as the vacuum pump removed the air
in the bell jar, there was less MEDIUM to convey the sound of the
ringing bell to the outside world - until there was no air left and
we couldn't hear the bell anymore.

The class was dumbfounded - and the teacher in awe. The teacher
congratulated the girl for her answer.

Then the teacher asked: "what happened when I opened the vent?"

The class dumb-guy yelled out with glee: "The Vacuum EX-CAPED!".

The expression on the teacher's face was PRICELESS!

UE,
K2EAA - TONY
NNNN
ZCZC


On 06/25/2015 08:55 PM, hwhall at compuserve.com wrote:
> Ieagerly await when we can 3D print vacuum tubes. And I'm really
> interested in how the vacuum gets applied.  ;-)
>
> Wayne
> WB4OGM

-- 
Never tell a young person that something cannot be done.
God may have been waiting for centuries for somebody
ignorant enough of the impossible to do that very thing.
                                      -John Andrew Holmes