Fwd: Pressure at nodes and antinodes

[David King]

>
> Graham,
>
> I too had been asked this question a while ago, but as I didn't  
> know and I didn't have one I forgot all about it.
>
> The following website, if correct, says you are right or wrong  
> depending on the pressure itself:
>
> http://www.fysikbasen.dk/English.php?page=Vis&id=6
>
> At the bottom of the article are some references -sadly the one  
> that looks most likely to explain the answer in detail is on the  
> aapt site and as I am not a member, I can't read it!
>
> Sorry
>
>
> David King
> Physics HoD
> Christ's College
> Private Bag 4900
> Christchurch
> New Zealand
>
>
>
>
> On 18/06/2008, at 6:40 PM, g.foster at clear.net.nz wrote:
>
>> Greetings Fellow Physies
>> We have just made a long metallic tube with a loud speaker
>> at one end and gas entry at the other. This enables us to
>> light the gas which comes through 1 mm holes 1.0 cm apart
>> and to produce single frequency sound at the other. The
>> flame pattern at resonance is one where we see high flames
>> at the antinodes and small flames at the nodes. Many of you
>> will have seen similar appartaus in photos.
>> However we are discussing why we get high and low flames and
>> we would appreciate clarification. If the high flames are at
>> the antinode this is where there is maximum variation in gas
>> pressure, so sometimes there is low pressure and at other
>> times a higher pressure than normal. At the nodes the gas
>> pressure remains constant at normal pressure and we think
>> that is where we get lower flames.
>> Question: Is a high flame produced at the antinode?
>> Our reasoning:
>> For at least half the time there is higher pressure than
>> 'normal'? Since the frquency for the best effect seems to be
>> 1 kHz to 2 kHz this would imply that there is higher than
>> usual gas pressure for at least 50% of the time and this
>> pushes more gas out the holes.
>> Comments please.
>>
>> Thanks
>> Graham Foster
>> EGGS Auckland
>>
>> Graham Foster
>> Director of Science, EGGS
>> AMI Learned Society
>>
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>

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