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Homework Help: Problem dealing with hook-law

  1. Nov 8, 2008 #1
    1. The problem statement, all variables and given/known data
    One end of a massless spring with hook-law constant K=119 N/M is epoxied to the bottom of a beaker. The other end of the spring is epoxied to a wooden block of mass m=4.17 kg and density 695 kg/m^3. THe beaker if filled with water until the block is fully immersed. Calculate the elongation of the spring. delta L= ??


    2. Relevant equations
    The equation I was trying to use was Fx=-kx
    I do not think this is correct because my answer was wrong.


    3. The attempt at a solution
    I put the data into the equation -k as -119 and x as 4.17 times 695 but in the end I still did not get delta L and that is what I need. I do not know where to begin with this problem.
     
  2. jcsd
  3. Nov 9, 2008 #2

    tiny-tim

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    Hi dban33! :smile:

    You've calculated the force by multiplying by the density

    but the lighter the block is, the stronger the force will be …

    so you should multiply by … ? :smile:
     
  4. Nov 9, 2008 #3
    Ok...so the lighter the block is...the stronger the force will be. Does that mean that for the equation F=-kx......im trying to solve for x right? because x is the elongation of the spring. This would mean that I would have to know the force of the block. Is the force of an object its mass times gravitational force?? F=mg?
     
  5. Nov 9, 2008 #4

    tiny-tim

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