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Homework Help: Length of Spring

  1. May 24, 2008 #1
    [SOLVED] Length of Spring

    1. The problem statement, all variables and given/known data

    A load of weight 400 N is suspended from a spring and two cords that are attached to blocks of weights 3W and W as shown. Knowing that the constant of the spring is 800 N/m, determine (a) the value of W, (b) the unstretched length of the spring.

    http://img406.imageshack.us/img406/472/13213uv7.jpg [Broken]

    2. Relevant equations

    [tex]F_{s} = -k x[/tex]

    3. The attempt at a solution

    I have already worked through part (a), getting 62.8 N for W and in the process I got 281.712 for the [tex]F_{s}[/tex] of the system above.

    Now from the picture above, I can figure that the length AB is 1110 mm using Pythagoreans. Whether that is relevant or not to figuring (b) out, I am not sure. I'm thinking that I need to find what the [tex]F_{s}[/tex] would be if there were no forces acting on the spring.
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. May 24, 2008 #2


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    Gold Member

    I would look at the relevant equation and attempt to determine if it can be expanded to include initial and final values.
    Last edited by a moderator: May 3, 2017
  4. May 24, 2008 #3
    You can determine angles using SOH CAH TOA. From there you can use components to work out your answer more precisely.
  5. May 25, 2008 #4
    double post...
    Last edited: May 25, 2008
  6. May 25, 2008 #5
    Thanks, I got it!
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