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!

Homework Help: Fluid Mechanics- Pressure on a gate

  1. Sep 16, 2012 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations


    Ycp=bh3/(12)(h/2)b + (h/2)

    3. The attempt at a solution

    I found the angle of the gate from the horizontal to be 53.1 degrees. Using this, I found y to be 2.5m and H (vertical distance to centroid) to be 6 m (2.5sin(53.1)+4).

    I then found Fw=9810*6*(4*5)=1177200N, and Ycp=(4*53)/(12*20*2.5) +2.5=3.33m.

    By taking the moment at the ground, I found Fw*(5-3.33)-5P=0, so P= 393kN. My book says the answer should be 523 kN. Help please.
  2. jcsd
  3. Sep 16, 2012 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    The picture does not show the angle P makes with the horizontal or vertical, so the question looks unanswerable to me. P could be an angle perpendicular to the 5m line or at some angle away from perpendicularity.
  4. Sep 16, 2012 #3
    I believe that P is supposed to be perpendicular surface (opposing Fw)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook