Date: Fri, 12 Nov 1999 14:29:08 -0700
Author: Jim Krider
Subject: RE: Resonance Demo
To see a video of the beaker resonating look at the Video Encyclopedia 9-06.
They used a strobe to show the deformations.
Jim Krider James.Krider@asu.edu
Physics and Astronomy Instructional Resource Team
Arizona State University Department of Physics and Astronomy
PO Box 871504, Bldg. PS Rm. F470,Tempe, Arizona 85287-1504
Phone: 480-965-8086 FAX: 480-965-7954
From: Russell Lawrence [mailto:firstname.lastname@example.org]
Sent: Friday, November 12, 1999 9:37 AM
Subject: Re: Resonance Demo
For what it is worth, I used an oscope and mic initially for this demo but
found that once I knew the resonance roughly I can do it quite repeatably
without the mic and oscope. In fact, I read that if you bend a piece of
paper and put it on the rim of the beaker (or wine glass), you can locate
the resonance by watching its vibrations (which are pressumably easier to
The improvement that I have not yet been able to achieve is enough
amplitude to shatter a beaker at more than about 2 cm. I keep thinking
that the way to do this is to buy expensive (instead of WalMart special)
wine glasses. (ie real crystal wine glasses).
Does anyone know at what distance the Memorex woman (the original, popular
human example of forced resonance ) was from the wine glass she shattered?
At 11:16 AM 11/12/99 -0500, you wrote:
>So sorry, but I am not convinced. I don't buy this idea. Did you see this
>demo actually break any glasses? I have been doing this demo for years.
>microphone and an oscilloscope are necessary to locate and lock the
>frequency, and also to show the class what happens to the phase shift and
>amplitude of the response from the glass. From your description one must
>the resonance peak simply by observing the beaker vibrations. This is not
>possible. And it does not show the class the phase and amplitude response
>the system to the driver.
>Resonance is typically 700 hz to 1000 hz depending on the glass. You
>see this vibration.
>Did you see this demo break a glass?
>At 01:10 PM 11/11/99 -0800, you wrote:
>>I need help in getting printed plans for making the following resonance
>>demo, which I saw at one of the conferences/workshops I attended in the
>>last two years (I can't remember exactly where or when):
>>The apparatus consists of a wooden box about the size of two shoe boxes
>>laid end-to-end. There is a speaker (possibly two) inside and the box is
>>divided into (3 or 4 ?) chambers. There is an opening or two facing
>>upward. There are two supports on which is placed a piece of (plate) glass
>>(about 2 feet long x 4-6 inches wide). The supports hold the glass about
>>1-2 inches above the box. As the frequency of the sound is adjusted, a
>>standing wave can clearly be seen to develop in the glass, and at the
>>right frequency the glass shatters.
>>This is more dramatic than the usual approach with speakers and a beaker
>>or wine glass. It is also easier to setup--no microphone and oscilloscope
>>are needed to tune the frequency. The sound does not have to be so loud as
>>to hurt the ears of those in the front row of the class.
>>If you have plans for this (including what kind of glass to use, which
>>is critical) or can refer me to someone who might be able to help, please
>>let me know.
>>St. Ignatius College Prep, San Francisco
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