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Homework Help: Physics problem -

  1. Aug 26, 2004 #1
    Physics problem - plz help!!!!

    I have absolutely no idea wat this question is talking about.
    Young’s modulus for bone is about 1.4 x 10E10 Pa, and bone can only undergo a 1.0% decrease in length before fracturing, so
    (a) What is the maximum force that can be applied to a bone whose minimum cross – sectional area is 3.0 cm², without fracturing? (This is the approximate area of the tibia at its narrowest).
    (b) What is the maximum height from which a 75kg person could jump without fracturing the tibia? Assume that stress is the same in both legs, and that the time between first touching the floor and coming to rest is 0.035s.

    Thanks for your help!!!
  2. jcsd
  3. Aug 26, 2004 #2
    Usually we need you to post your work on a problem before we help out.

    However, I think I might be able to steer you in the right direction.

    Remember that Young Modulus is defined (one dimensionally) as :

    Y (or E) = stress/strain

    Where stress is Force/Area(cross sectional)

    and strain is (change in length)/(original length)

    For part a you are given all of these but the force.
    All you need to do is plug your values in.
  4. Aug 26, 2004 #3
    As a suggestion you can use Newton's 2nd Law and Conservation of Energy to get the height for part b. Do you know what the answer should be?
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