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Vibrations in a glass with water.

  1. Nov 21, 2015 #1
    So I just poured water in a glass to clench my thirst. Hit the 2/3 empty glass with a pen and a high frequency started resonating for a brief moment, wich I percepted as sound. When I tilted the glass the tilt resulted in change of frequency. When the glass was empty there was no change in frequency. The frequency did not change when the glass was rotated in such manner that the water did not change it's horizontal positioning or not atleast in a way that was observable by ear.
    This left me thinking that the vertical movement of the water interfiered with the resonance of the glass, "damping" the vibrations at the direction of the tilt. But at the same time the horizontal tilt is releasing vertical space in the opposite direction of the tilt. So this does not make much sense, does it?

    Then I'm left wondering how the series of vibrations are perpendicular to the glass or am I looking at this from a completly wrong angle? Or is the work done from the force behaving like a wave? I have a tiny tickle of this but I could be so wrong, afterall having nearly no education in physics.
    I've just started dabbling in Fourier Series by Georgi P. Tolstov, starting with introduction to real analysis by A.N.Kolmogorov & S.V.Formin, wich is way ahead of me considering that I have not yet finished the book on fundamental concepts of algebra wich I find easily understandable.

    TL;DR: A glass is filled with an unsubstantial amount of water. When I tilt the glass that as been struck with force. Why does the frequency of the resonation change.

    I did not take to my count that the water also forwards the force. But I'll leave this queston to you for now.

    Kind regards; Observeraren
    Last edited: Nov 21, 2015
  2. jcsd
  3. Nov 21, 2015 #2


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    I think you meant quench

    this doesn't sound correct as it goes against having glasses filled with different levels to produce different tones
    note ... along with different water levels different sizes are also used

    also a single glass with different levels

    that would be expected as you are changing the shape of the resonant chamber

  4. Nov 21, 2015 #3


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    I haven;t formulated an answer yet, but a good start would be to take into account the form of vibrations in a hollow cylinder.

    This is a crude online image I found but it makes the point.

  5. Nov 21, 2015 #4


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    Nono. He meant clench.o0)

    I think you misinterpreted that. I believe he meant his empty glass did not change frequency when tilted versus untilted.
  6. Nov 21, 2015 #5


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    ahhh yes on that point agreed I probably misread

    but the partly filled tilted and untilted will make a change

  7. Nov 21, 2015 #6
    Yeah! That was definitly the word I was after.

    Well this sums up the change in frequency for me!
    From the right-hand drawing I interpret the crest of these vibrations to be perpendicular to the glass. Is this the case?


    EDIT: It's 1:32AM over here. Thanks for the discussion so far! Good night!:sleep:
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