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Homework Help: What is the spring constant of spring?

  1. Mar 4, 2012 #1
    1. The problem statement, all variables and given/known data
    A 60 kg person drops from rest a distance of 1.20 m to a platform of negligible mass supported by a stiff spring. The platform drops 6 cm before the person comes to rest. What is the spring constant of spring?


    2. Relevant equations



    3. The attempt at a solution

    w=1/2kx^2

    mgh=1/2kx^2

    2(mgh)/x^2=k

    2(60kg*9.8*1.20)/0.06m=3.92*10^5

    the answer however is 4.12*10^5


    What am I doing wrong?

    Thank you
     
  2. jcsd
  3. Mar 4, 2012 #2

    Delphi51

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    The mass falls further than 1.20 as the spring compresses.
     
  4. Mar 4, 2012 #3
    So would I add the 0.06m? Iam a bit confused
     
  5. Mar 4, 2012 #4

    tiny-tim

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    Correct. :smile:

    The question says …
    … after that it drops a further 0.06 m, so the total drop (for the person) is 1.26 m :wink:
     
  6. Mar 4, 2012 #5
    Thx Tim
     
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