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Homework Help: Cross section help on compression calc

  1. Jun 21, 2011 #1
    1. The problem statement, all variables and given/known data

    The Femur bone in the human leg has a minimum effective cross section of about 3.0 cm2 How much compressible force can it withstand before breaking

    2. Relevant equations

    Compressive Strength (bone)(N/m2) = 170 x 106
    P = F/A

    3. The attempt at a solution
    Not sure what a cross section is exactly, how should A in formula Stress = F/A be written when they state 3 cm2 cross section.
    A = PI*R2

    which one do I use for R
    A = .0152
    A = .03
    A = .032

    170 x 106 = F / .03m2
  2. jcsd
  3. Jun 21, 2011 #2
    The A in the formula is the cross sectional area. The cross section is a "slice" of the object in question. For example, if you cut into an apple, the resulting flat shape you see would be a cross section of the apple.
  4. Jun 21, 2011 #3
    3.0cm^2 * (1m/100cm)^2 = 0.0003m^2 which is the cross sectional area of the bone.
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