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Air pressure needed for ballast

  • Thread starter doodles
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  • #1
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A submarine is submerged to a depth of 3150 ft in the Atlantic Ocean. What air pressure (in kpa) is needed to blow water out of the ballast tanks?

I know the answer is 9410 kpa but I have been going in circles trying to figure this out.

P=hd using seawater density of 64.0 pound feet cubed did not work for me.

Thanks for helping:)
Doodles
 
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Answers and Replies

  • #2
ideasrule
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Let's work in metric units. P=rho*g*h, and you know all three variables, so you can find P. That's the pressure exerted by the water. You have to add on the pressure exerted by the atmosphere, and that's your answer.
 
  • #3
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Thanks Ideasrule:smile:

P=1000kg/m^3(9.801m/s^2)(3150ft)(1/3.281ft)=9409676.928 pascals= 9410kpa

I made a mistake and was using 9.81m/s^2 instead of 9.801m/s^2

I still cant figure out how I got pascals out of kg/m^3 s^2 any suggestions? These type of conversions get tricky.
 

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