From: Damon Jansen (dkjansen@yahoo.com)
Date: Wed Feb 25 2004 - 17:01:42 PST
Message-ID: <20040226010142.89368.qmail@web11507.mail.yahoo.com> Date: Wed, 25 Feb 2004 17:01:42 -0800 (PST) From: Damon Jansen <dkjansen@yahoo.com> Subject: sound vacuum
Howdy pinhole folks,
A teacher friend of mine gave me this scenario and I
was wondering what you thought.
She is teaching a 3rd grade class and they have done a
number of activities seeing a number of materials that
sound will travel in: air, water, wood, and others.
However, as they are wrapping up their investigations,
she is realizing that the part where they learn that
sound cannot travel through a vacuum is just something
she is telling her students. She would like to be
able to show this.
So, I know the standard demo to show this is the bell
in a bell jar that you remove air from. I also have
read a few critiques (including the "Physics Begins
with an M..." book) arguing that this demo is
demonstrating a large impedance mismatch between glass
and the rarified air inside and does not create nearly
the vacuum required to show sound not traveling
through air. I have not done the experiment, but they
argue that if you put a microphone INSIDE the bell
jar, it can pick up the sound of the bell.
So my questions:
1. Is there a demonstration that actually does show
that sound cannot travel in a vacuum that could be
done in a 3rd grade class. (We do have access to high
school physics lab stuff.)
2. If there is not a good demonstration, if we did do
the bell jar demo, what could we say about it that
would help the third-grade students' understanding but
was not wrong?
thanks,
damon
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