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Homework Help: Radius Problem

  1. Feb 9, 2008 #1
    [SOLVED] Radius Problem

    A brass rod (density = 8470 kg/m3) is 12cm long and weighs 20N. What is the radius of the rod?



    I'm confused when finding area. I don't think I'm using the right variables.



    volume = mass/density
    v = 2.04 kg / 8470 kg/m3 = 2.4X10^-4

    Area = volume/length?
    A = 2.4X10^-4 / .12m = .002m
    A = pi r^2
    r = .03m
     
  2. jcsd
  3. Feb 9, 2008 #2

    malawi_glenn

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    Area is measured in m^2

    And where did you have any troubles? Just do unit analysis to make yourself sure.
     
  4. Feb 9, 2008 #3
    Yeah I forgot to complete the area units, sorry.
    I didn't think area = volume / length was the right equation.
    If it is then I have the right answer already, right?
     
  5. Feb 9, 2008 #4

    malawi_glenn

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    ok, then I see. Yes the volume of a cylinder / rod is area x lenght.
     
  6. Feb 9, 2008 #5
    Ah, then I just questioned myself for no reason. I already had the correct answer.

    Correct?
     
    Last edited: Feb 9, 2008
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