1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Pressure at water tank

  1. Jun 18, 2016 #1
    1. The problem statement, all variables and given/known data
    i am asked to find the value of y in this question . I am not sure should i consider the atmospheric pressure acting on the mercury or not .

    2. Relevant equations

    3. The attempt at a solution
    i choose to consider the atmospheric pressure as 0 in this case . So , my working is 30000 + (1.5x820x9.81) + (5 x1000x9.81) =13600(9.81)y , where y = 0.68m , am i right ? btw , i am not very sure about whether the pressure of water is (5 x1000x9.81) or not , because the outlet is not at bottom of teh tank , can someone exp;lain pls ?

    Attached Files:

    • 223.PNG
      File size:
      3.5 KB
  2. jcsd
  3. Jun 18, 2016 #2


    User Avatar
    Science Advisor

    If the pipe were even lower than the 1m shown (say 100m lower) would the pressure at the water-mercury interface be affected? So should you account for that 1m height by adding it to the 5m?

    Wether you can ignore atmospheric pressure depends on if the pressure gauge is showing absolute pressure or pressure relative to atmospheric ('gauge' pressure).
  4. Jun 18, 2016 #3
    i think the extra 1m should take into consideration , am i right ? so , the working should be 30000 + (1.5x820x9.81) + (6 x1000x9.81) =13600(9.81)y ?
  5. Jun 18, 2016 #4

    rude man

    User Avatar
    Homework Helper
    Gold Member

    OK if the 30 kPa is gauge pressure.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted