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Area of a cross section

  1. Apr 17, 2005 #1
    I'm going through my intro to mechanical engineering material and there was one thing I was never clear on:

    If you have a cross section of a rod, why isn't its' area at a cross section [tex]pi * r^2[/tex] as a opposed to [tex]piD^2/4[/tex], where D is the diameter?
  2. jcsd
  3. Apr 17, 2005 #2


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    Becasue people are actually measuring the diameter...?

  4. Apr 17, 2005 #3
    whoops. That makes sense :D
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