1. Not finding help here? Sign up for a free 30min 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!

Fluid Motion

  1. Nov 15, 2006 #1
    Ok, Air flows through this tube at a rate of 1200 cm^3/s. Assume that air is an ideal fluid.
    What is the height h of mercury in the right side of the U-tube?
    Here's a picture:

    First, I found the velocity of the air in the 2 cm and 4 mm tube.
    In m/s, for the 2cm, i came up with 1200/(1000000pi(.01^2))
    and for the 4mm 1200/(1000000pi(.002^2))
    Then, I plugged it into bernoulli's equation, with the density of air as 1.2 kg/m^3. This gave the 2cm tunnel to have 5462.5 less pascals than the other 4 mm tube.
    Then, using 13540 for the kg/m^3 of Hg, and setting the pressures of the two sides equal, I came up with:
    5462.5 = 13540 (9.8) (h), which gave me h= .0412 m, or 4.12 cm, which is wrong. Anybody know what I did wrong?
  2. jcsd
  3. Nov 16, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper

    I'm not seeing a problem with what you did. Do you know the answer that is expected?
  4. Nov 16, 2006 #3
    I wish I knew the answer that is expected :P Do you know if those are the right densities I used in kg/m^3?
  5. Nov 16, 2006 #4
    Found out I was using the wrong densities ^^ I used 1.3 kg/m^3 for air and 13700 for Hg and got the right answer. My physics book is too big to bring home, so I rely on google for my constants :(
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Fluid Motion
  1. Fluids in motion (Replies: 6)

  2. Fluid motion (Replies: 3)