1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question (body immersed in fluid)

  1. Mar 22, 2012 #1
    Hi all

    Can please check my answer in this Question ?
    and Is my diagram correct ?

    http://store2.up-00.com/Mar12/PD451302.jpg [Broken]

    thanks
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Mar 23, 2012 #2
    where are you ?
     
  4. Mar 23, 2012 #3
    Do you have the plate upside down?
     
  5. Mar 23, 2012 #4
    you mean that diagram is wrong ..
     
  6. Mar 23, 2012 #5
    Problem states base is 4 m long. It is not 1 m from surface...the way you have it drawn.
     
  7. Mar 23, 2012 #6
    As Problem state the base of triangular is four m while the height is 6 m ... and from free srface is immersed at the one m
     
  8. Mar 23, 2012 #7
    Now is the diagram correct

    http://store2.up-00.com/Mar12/NjT38265.jpg [Broken]
     
    Last edited by a moderator: May 5, 2017
  9. Mar 24, 2012 #8
    Yes, the sketch is now correct.
     
  10. Mar 24, 2012 #9
    ok what about other answers
     
  11. Mar 24, 2012 #10
    You should rework the problem. Let's see your work.
     
  12. Mar 24, 2012 #11
    p = pgh
    = 900 X 9.81 X 3
    = 26.5

    but the unit here is kpa or N/m^2

    Now center of pressure
    = (IG / AX ) + X

    = bh^3/36 = (4X 6^3) / 36 = 24

    so now (24/12X 1 ) +

    = 5
     
  13. Mar 24, 2012 #12
    When the problem says "determine the total pressure", it is unclear whether they are seeking the total pressure force due to the pressure at a designated point.

    The designated point is generally the center of mass of the triangle. You have not calculated that. The center of pressure is a function of the moment of inertia, the area, and the center of gravity of the plate.

    So you need to compute those three items first. Your moment of inertia is incorrect.
     
  14. Mar 24, 2012 #13
    Is the plate not fully submerged? Did you quote the problem statement exactly?
     
  15. Mar 24, 2012 #14
    yes plate fully submerged

    The center of pressure is located at the centroid of the triangular shaped pressure field 2/3 from the top of the water line."

    From this I may compute:

    1 + 2/3 .6 = 5
     
  16. Mar 25, 2012 #15
    The location of the centroid is 1/3 the distance from the base of the triangle to the apex opposite the base along the height of the triangle. What is the height (altitude)? Ybar=h/3. First you must determine h, then add the 1.0 to it.
     
  17. Mar 26, 2012 #16
    I have a little difficulty

    seeee...........

    Now I want know Xbar is 3 or 5 ?

    I will try ...

    presure = pg(xbar)

    = 2.6 kpa


    ----------------
    2)
    Center of pressure

    Center of pressure =( IG/Area(xbar) ) = xbar
    IG = bh^3/36
    IG = 4 X 6^ / 36 = 24

    Area = 1/2 X 4 X 6
    = 12 m^2

    Now ..
    Center of pressure = (24 / 12 X 3) + 3

    = 3.6 m


    pleeeeeeeeeeeeese help me now what is the wrong ..
     
  18. Mar 26, 2012 #17
    You calculation for center of pressure looks good except for round off error. I get 3.66 which rounds to 3.7 m for the center of pressure. You use the distance that the centroid of the triangle is below the surface for the calculation. It is 3 m.

    Your pressure computation is off by a factor of 10. It should be 26 KPa.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Question (body immersed in fluid)
  1. Fluid Question (Replies: 11)

  2. Fluid Question (Replies: 21)

Loading...