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!

Mass flux through a kidney

  1. Sep 30, 2012 #1
    1. The problem statement, all variables and given/known data

    Water enters a kidney through a tube at 10 mL/min. It exits through a 6-mm-diameter tube at 20 mm/s.What is the rate of change of mass of water in the kidney?

    2. Relevant equations


    After conversions to meters
    A=(pi/4)*.006^2 = .0000282

    3. The attempt at a solution

    dm/dt=.165 kg/s

    Needless to say, thats not the right answer, but I can't figure out where I went wrong.
  2. jcsd
  3. Oct 1, 2012 #2
    You are incorrectly finding the positive flux. It is 1.67*10^-4 for the inflow and 5.655*10^-4 for the outflow.

    Inflow 10 mL/min * (min/60 s) * (1 cm^3/mL) * (m^3/1000000 cm^3) = 1.67*10^-7 m^3/s

    Outflow=V*A { 20 mm/s * (m/1000mm) } * { [(6 mm/2)/1000]^2 * pi } = 5.65*10^-7 m^3/s

    Δm = -density*Q(in) + density*Q(out)
    = [-1000*.000000167]+[1000*.000000565]
    = 3.99*10^-4 kg/s
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Mass flux through a kidney
  1. Flux through a cube (Replies: 3)