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How can I calculate underwater pressure quickly

  1. Jul 14, 2015 #1
    Does anyone know a simple formula to calculate underwater pressure?
     
  2. jcsd
  3. Jul 14, 2015 #2

    Doc Al

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  4. Jul 14, 2015 #3
    I have the formula "P=r*g*h" when r=fluid density, g=Acceleration of gravity and h=height of fluid.

    Got this off NASA
     
  5. Jul 14, 2015 #4

    Doc Al

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    Same thing. (##\rho## is the common symbol for density.)
     
  6. Jul 14, 2015 #5

    Bandersnatch

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    The simplest way you can get is 1 extra atmospheric pressure per 10 metres of water column.
     
  7. Jul 14, 2015 #6
    Brilliant, that's just what I was looking for! :-)
     
  8. Jul 14, 2015 #7
    How much Is normal atmospheric pressure?
     
  9. Jul 14, 2015 #8

    Bandersnatch

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    1 atm or very close to 1 bar, or very close to 100 000 Pascals.

    In the spirit of the forum I'd encourage you to take the earlier-posted equations and plug in the numbers for 10 metres of water, and see if it really comes down to 100 000 Pascals. You need density of water in kg/m^3.
     
  10. Jul 14, 2015 #9

    Nugatory

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    Of course Bandersnatch's answer is an approximation - but quite good enough for all practical purposes. It would be a good exercise to calculate exactly what the pressure increase from ten meters of water is using the ##\rho{g}h## formula - google will find the values of the various physical constants you'll need - and see just how good of an approximation it is, whether it is sensitive to small changes in the temperature of the water.
     
  11. Jul 14, 2015 #10
    Thanks:-)
     
  12. Jul 14, 2015 #11
    Just wandering if there are any other formulas for it?!
     
  13. Jul 14, 2015 #12

    Nugatory

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    ##\rho{g}h## is pretty much the gold standard here. You can make additional corrections if ##\rho## or ##g## aren't constant, but for any problem involving reasonable liquids on or around the surface of the earth, these are just rounding errors.
     
  14. Oct 2, 2015 #13
    Hey guys I've collected some information and I can now calculate "P=r*g*h" It is:

    999.99 X 9.81 X 11000 = 107 908 920.9
    Fluid Density X Acceleration Due To Gravity X Height Of Fluid = Pressure

    But this is it pascal, does anyone know the conversion rate from pascal to bar???
     
  15. Oct 2, 2015 #14

    Doc Al

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    1 bar = 100,000 Pa.
     
  16. Oct 2, 2015 #15

    russ_watters

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    While we appreciate the traffic, Google will answer these questions in milliseconds...
     
  17. Oct 2, 2015 #16

    DaveC426913

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    And don't forget what 'snatch said: "1 extra atmospheric pressure per 10 metres".
    People often forget there's an initial 1 atm at sea level.
     
  18. Oct 2, 2015 #17

    russ_watters

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    That often falls out of the analysis (for example, for a submarine), but yes, that thought should at least be processed at the start of the analysis.
     
  19. Oct 2, 2015 #18
    But it's not as friendly and it doest'n give you a straight answer
     
  20. Oct 2, 2015 #19

    russ_watters

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    It certainly has its limitations, but it is a life-skill everyone should have.
     
  21. Oct 2, 2015 #20

    billy_joule

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