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Conservation of momentum ; spring ; friction

  1. Nov 25, 2008 #1
    1. The problem statement, all variables and given/known data
    [​IMG]

    I need help with part 2 of the problem, which asks to find the maximum compression of the spring. I have already found the work done by friction in part 1.


    2. Relevant equations

    I know momentum is conserved (duh) and so is energy, although some of both are lost to friction. I really do not know how to get started with this.


    3. The attempt at a solution

    I attempted setting some equations equal to each other, yet none seem to make sense. I feel helpless without the spring constant. K is not given.

    I attempted creating a total conservation formula, yet to no avail. I am clueless how to incorporate friction, energy, and/or momentum together to find [tex]\Delta[/tex]x - compression

    HELP PLEASE :cry:
     
  2. jcsd
  3. Nov 26, 2008 #2
    Well neither momentum nor energy is considered conserved in this problem, because the system of block and spring lose energy to heat the universe outside the system.

    If you have determined the energy lost to friction in part 1, you know this is equal to the frictional force times the distance applied. so the maximum compression is 1/2 the energy lost divided by the frictional force.
     
  4. Nov 26, 2008 #3
    oh god! thank you so very much

    didn't know why i didn't think of that :] I got the answer right!
     
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