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Homework Help: PE problem

  1. Oct 20, 2005 #1
    I just need to make sure I understand how to do this and that I am doing everything correctly. Could someone check my work please?

    You place the spring vertically with one end on the floor. You then drop a 1.70 kg book onto it from a height of 0.70 m above the top of the spring. Find the maximum distance the spring will be compressed.
    k_1 + U_1 + W_{other} = k_2 + U_2
    I have that

    k_1=0, U_1= mgy_1, W_o=0, k_2=0, U_2=1/2kx^2

    So the issue is that I have to the potential energy to the start of the spring plus the distance the spring compresses.

    To solve this I need to adjust the equations to look like


    This works out to a homogenous quadradic that looks like


    Plugining in values and solving gets me

    0.142 meters.


  2. jcsd
  3. Oct 20, 2005 #2


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    Homework Helper

    You didn't include the spring constant, so I can't check your arithmetic, but your reasoning looks faultless to me. Good job. :)
  4. Oct 21, 2005 #3
    oops...sorry about that.

    It should be 1400N/m...and thanks :smile:
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