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Thrust on immersed surfaces

  1. Feb 2, 2013 #1
    A fuel tank contains oil of a relative density of 0.7 on one side there is a circular trap door of 1.8m in diameter. The fuel level is 1.8m above the top edge of the door calculate the thrust on the door.
  2. jcsd
  3. Feb 2, 2013 #2


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    Welcome to PF!

    Hi Twowaypower! Welcome to PF! :wink:

    Show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
  4. Feb 2, 2013 #3
    I tried using
    P=pgh. Which works out as 700*9.81*3.6= 24.7212kN
    Then thought many had to put that int P=FA. Which as area is Pi r^2 area works out as 2.54m^2
    That gave me 62.7918kN.
    I have used 1/2pgbh^2 to find out thrust on submerge rectangular objects but couldn't make that one work either. The answers in my book is 47.2 kN but I just can't get it.
  5. Feb 2, 2013 #4


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    Hi Twowaypower! :smile:

    Hint: 47.2/62.7918 = 3/4 :wink:
  6. Feb 2, 2013 #5
    I was scratching my head for so long and it was so obvious. Thank you. Really need that.
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