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Poiseuille's Law

  1. Jan 29, 2004 #1
    Trouble with a problem. What is the flow rate if a tube consists of two sections, the first with a length of 20cm and radius 0.15cm and the second part with length 1.0cm radius 0.05? with a pressure difference across the entire tube of 3cmHg (p1-p3). (viscosity = 0.801 cP)

    I've tried this and end up with two many unknowns and not enough equations. Can anybody help?
  2. jcsd
  3. Feb 1, 2004 #2
    [tex]\dot V = \frac{\pi \, r_1^4}{8\,\eta}\frac{p_3-p_2}{l_{32}}[/tex]
    [tex]\dot V = \frac{\pi \, r_2^4}{8\,\eta}\frac{p_2-p_1}{l_{21}}[/tex]
    Well, just solve this for p2 und dV/dt and you have your result :)
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