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Homework Help: Free Fall Acceleration fractures Problem

  1. Sep 8, 2008 #1
    1. The problem statement, all variables and given/known data
    Falls resulting in hip fractures are a major cause of injury and even death to the elderly. Typically, the hip’s speed at impact is about 2.0 m/s. If this can be reduced to 1.3 m/s or less, the hip will usually not fracture. One way to do this is by wearing elastic hip pads.

    If a typical pad is 5.0 cm thick and compresses by 2.0 cm during the impact of a fall, what acceleration (in m/s^2) does the hip undergo to reduce its speed to 1.3 m/s?

    2. Relevant equations
    (y1-y0)=(Vf^2-V0^2)/2a


    3. The attempt at a solution
    y1-yO=-2 cm = 0.02M Vf= 1.3 V0=2.0 a=?
    1.3^2-2.0^2 =-2.31

    (-2.31m^2/s^2)/ 2*-0.02m =a a= 57.75m/s^2

    question is......did i do this problem right because this is an online hw problem and i keep getting it wrong so i'm wondering if it is the program or if it just me.

    thanks
     
  2. jcsd
  3. Sep 9, 2008 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Hi tater08! :smile:

    Your answer looks fine to me! :smile:

    I think it must be a misprint …

    hmm :rolleyes: … try using 3.0 cm instead of 2.0 cm, and see if the computer accepts that! :smile:
     
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