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Blood circulation problem

  1. Aug 26, 2009 #1
    1. The problem statement, all variables and given/known data

    The blood transports substances required by the body and the waste products of metabolism. The blood contains many different constituents including red blood cells, white blood cells, platelets and protein. However, for calculation purposes, it is sufficient to treat blood as a uniform liquid with viscosity = 2.95×10−3 Pa.s and density = 1050 kg/m^3 at normal body temperature. The aorta is the principal blood vessel through which blood leaves the heart in order to circulate around the body. The average radius of the aorta is R(a) = 1.20×10−2m , the average length is L(a)= 0.210m and the volume flow rate is Q(a)= 5.40 L/min The blood circulates very slowly at V(c) = 3.75×10−4 m/s through many small blood vessels called capillaries. The average radius of a capillary is R(c)= 4.00×10−6 .

    a) Calculate the average speed of the blood though the aorta.
    b) Calculate the average speed of the blood though the aorta.
    c) Calculate the average power supplied in maintaining the blood flow through the artery.

    *net force to drive blood through the aorta is (the pressure drop along the aorta)*(the area of the aorta).

    2. Relevant equations

    h=2ycos(@)/pgr y= force tension p = density of liquid g=gravity =9.81 r = radius

    y= F/l F=force l= length (i think)

    P(i)-P(o) = 2y/r = 4y/r = y/r ( 3 different equations)

    3. The attempt at a solution

    I have no clue which equation to use to find the a,b,c...

    i dont even know how to begiin..
  2. jcsd
  3. Aug 26, 2009 #2


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    Hi abcphysics123! :smile:

    (erm :redface: … what's the difference between a and b?! :confused:)
    Be logical! :wink:

    What is volume flow rate?

    Volume flow rate = volume per second

    = area times distance per second

    = area times speed :smile:
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