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Homework Help: Calculating the max distance of compression of the spring HELP

  1. May 16, 2010 #1
    Calculating the max distance of compression of the spring plz HELP!!

    1. The problem statement, all variables and given/known data
    A 2.0 kg block is dropped from a height of 40 cm onto a spring of force constant k = 1960 N/m. The maximum distance the spring is compressed is?


    2. Relevant equations
    I Used the equation W=mgh and W=1/2kx^2..


    3. The attempt at a solution
    i did..
    W=2*9.8*0.4
    =7.84

    then i used
    7.84=1/2*1960*x^2
    from which i got x=0.0894427191
    then i did
    7.84*0.0894427191=0.7012309177
    then i did
    7.84-0.7012309177=7.13879

    can anyone plz help me tel where i went wrong? because the answer to this question is 10 but i dont know how to get it..plz help=].
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 16, 2010 #2
    Re: Calculating the max distance of compression of the spring plz HELP!!

    There is extra gravitational potential energy from the distance through which the spring drops through while touching the spring. In other words, the total distance that the object drops is 40 cm plus however far the spring compresses.
     
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