Physics of snapping the fingers

Discussion in 'Physics & Math' started by dristam, Mar 15, 2009.

  1. dristam Registered Senior Member

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    Everyone thinks I'm nuts but I'm still clinging to the notion that (perhaps) the loud sound of snapping one's fingers results from exceeding the Speed of Sound. I've heard that the crack of a whip's tip is so caused and I think a human finger can also duplicate the feat. Naysayers mainly retort that the sound is produced by the middle finger HITTING the base of the thumb, but I don't believe it. One such naysayer told me to place a wadded napkin over the base of my thumb to deaden the sound and thus disprove my assertion. I did the test and the sound was NOT deadened, so I remain unswayed.

    I figure that only a super slow-motion camera could truly pin down what velocities are being attained. I don't have the means for that. Any ideas?
    :shrug:
     
  2. rpenner Fully Wired Valued Senior Member

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    3,184
    In multiple trials, placing something between finger and meaty part of thumb altered the sound. So my experiments support the no-sonic-boom theory. A laminated 3x5 card seems to increase the noise as expected by noise-upon-impact theory.

    Here's a video at 2000 frames per second. You can see the meaty quiver of the sounding board base of the thumb.

    http://courses.ncssm.edu/hsi/hsvideo/snap.htm
     
  3. Anti-Flag Pun intended Registered Senior Member

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    3,714
    Agreed, the noise comes from your finger hitting the base of the thumb. Not sure dristam how you're experiment failed this but you should repeat it.
     
  4. dristam Registered Senior Member

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    Thank you for that video!

    It appears to show the fingertip moving at merely 15 or 20 miles per hour, (about 2.5 inches in a hundredth of a second). Would others agree?

    But I am sorely disappointed.

    Oh well
     
  5. draqon Banned Banned

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    35,006
    dude, if it moved at speed of sound...you wouldnt have a finger left.
     
  6. dristam Registered Senior Member

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    I'm minimally embarrassed to add that I'm still not convinced. However, I would definitely be convinced if there were such a video with a mic positioned very very near that is connected to a visualizer or oscilloscope.

    Maybe it's not the movement of the middle finger but the sudden shudder of the thumbnail I dunno, I'm nuts
    :shrug:
     
  7. dristam Registered Senior Member

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    Nevermind, I think I'm convinced now uh maybe.
    The odd noise could derive from the all-of-a-sudden shrinking orifice formed between the digits, and the bland hitting noise is thereinthrough channeled. Could be.
     
  8. Oli Heute der Enteteich... Registered Senior Member

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    11,890
    Where would the requisite energy come from to accelerate the digit(s) to sonic speed?
    Could the bone structure survive the acceleration?
    It is NOT a result of a sonic boom.
     

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