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Transmission delay of pressure in a fluid

  1. Apr 18, 2012 #1
    I would like to know if the transmission delay of pressure give a differential force on an object ? Example: an object in water, we put pressure with mass over water at right at t=0s. The pressure at right is faster on the right side than the left side (d1<d2). The object seems to move with a force in water. The delay is very small but exist. Is this true ?
     

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  3. Apr 18, 2012 #2

    boneh3ad

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    In water, there is effectively no delay since the medium is incompressible. For something like air, which is compressible, this can happen.
     
  4. Apr 18, 2012 #3
    See section on speed of sound in water in http://en.wikipedia.org/wiki/Speed_of_sound
    Although the sound pressure wave may arrive at the two sides of an object at different times, if it is a sine wave, the net force difference over a full cycle is zero.
     
  5. Apr 18, 2012 #4

    AlephZero

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    The speed of sound in water is about 1500 m/s compared with about 340 m/s in air. Whether you think that is fast enough to ignore depends on the situation. Sonar woudn't work in a truly incompressible fluid, for example.
     
  6. Apr 18, 2012 #5

    boneh3ad

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    Fair enough. I can't argue with facts.
     
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