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: Specific Gravity and Pressure in Flowing Pipe

  1. Jun 6, 2010 #1
    1. The problem statement, all variables and given/known data

    The following question is from ExamKrackers Physics [an MCAT prep book].


    An ideal fluid with specific gravity of 1.0 is passed through a pipe. Along the length of the pipe shown above are attached 3 vertical pipes which are sealed off as shown above. If now a different ideal fluid with a specific gravity of 2.0 is passed through the pipe at the same volume flow rate the pressure at any point in the pipe would:

    a. decrease by a factor of 2
    b. remain the same
    c. increase by a factor of 2
    d. more information is required

    2. Relevant equations

    K = P + pgy + 1/2*pv^2

    3. The attempt at a solution

    Based on bernoulli's equation above if you increase rho, pressure would have to decrease since the terms of bernoulli's equation sum to a constant. The answer given by Examkracers is that [c] the pressure increases by a factor of 2. I can't seem to see why this would be true. Any help would be greatly appreciated.
    Last edited: Jun 6, 2010
  2. jcsd
  3. Jun 6, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Maneuver1! Welcome to PF! :smile:

    (have a rho: ρ and try using the X2 tag just above the Reply box :wink:)
    I think you're both wrong …

    Bernoulli's equation is constant along a streamline

    unless you know something about the starting (or finishing) conditions, I don't see how you can say anything about the pressure :confused:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook