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Determine the temperature of the blood/ Heat problem

  1. Mar 29, 2006 #1
    Blood can carry excess energy from the interior to the surface of the body, where the energy is dispersed in a number of ways. While a person is exercising, 0.8 kg of blood flows to the surface of the body and releases 2050 J of energy. The blood arriving at the surface has the temperature of the body interior, 37.0°C. Assuming that blood has the same specific heat capacity as water, determine the temperature of the blood that leaves the surface and returns to the interior

    ok..I know that DELTA T = Q/cm
    Q= heat
    since i dont have the heat..i had to find it...so i did this
    Q=( CM ) ( DELTA T ) = ( 4186 ) ( .8 ) ( 37.0 °C - 15.0 °C )
    = 73673.6 J

    now I got the heat...so i can apply this formula to find the temperature..
    DELTA T = Q/cm = 73673.6 / ( 4186 ) ( .8 ) = 22 °C
    but still..i keep getting it wrong...:mad: :confused: ..does any one knows what im doing wrong ??..
     
    Last edited: Mar 29, 2006
  2. jcsd
  3. Mar 29, 2006 #2

    Doc Al

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    Staff: Mentor

    What do you mean you don't have the heat? The problem stated: "0.8 kg of blood flows to the surface of the body and releases 2050 J of energy."

    Where did you get the 15.0 °C ? (The final temperature of the blood is what you are trying to find.)
     
  4. Mar 29, 2006 #3
    ok.....so it should be
    2050 / ( 4186 ) ( .8 ) = 0.612
    BUT IT STILL WRONG.....

    ok..is it 37.612 ?
     
    Last edited: Mar 29, 2006
  5. Mar 29, 2006 #4

    Doc Al

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    What did you get for the temperature of the cooled blood?
     
  6. Mar 29, 2006 #5

    Doc Al

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    You're getting closer... remember that heat is being removed from the blood.
     
  7. Mar 29, 2006 #6
    36.388:biggrin:
     
  8. Mar 29, 2006 #7
    thanx alot Dr Al :smile: :approve:
     
    Last edited: Mar 29, 2006
  9. Oct 20, 2008 #8
    I have a similar problem to this but I don't understand it. Where did you guys get the 4186?


    (the problem I have is...Blood can carry excess energy from the interior to the surface of the body, where the energy is dispersed in a number of ways. While a person is exercising, 0.6 kg of blood flows to the surface of the body and releases 2000 J of energy. The blood arriving at the surface has the temperature of the body interior, 37.0°C. Assuming that blood has the same specific heat capacity as water, determine the temperature of the blood that leaves the surface and returns to the interior... so basically same thing, just different numbers)
     
  10. Oct 20, 2008 #9

    mgb_phys

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    It's the specific heat capacity of water, it takes 4186J of energy to raise the temperature of 1kg of water through 1 Kelvin (or 1deg C).
    You have to know/look this up, it's an experimental value.
     
  11. Oct 20, 2008 #10
    Thank you, mgb_phys! I get it now! :smile:
     
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