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Mechanics Elastic springs question

  1. Oct 19, 2009 #1
    A particle of mass m is attached to one end of an elastic spring of natural length l and modulous lambda ..The particle and spring rest on a rough horizontal surface and the other end of the spring is fixed..Th coefficient of friction is mu .the particle is held at rest with the spring compressed to a length 2/3l and then released.Show that the particle is instamtenously at rest when it has a moved a distance x where,..lambda=Y,mu=P
    [itex]x=\frac{2Yl-6Plmg}{3Y}[/itex]

    Can some one check if my assumptions are right?..

    First of all they want me to show the velocity is 0..
    I use conservation of energy
    [itex]\frac{Yl}{18}=\frac{Yx_1^2}{2l}+\frac{1}{2}mv^2[/itex]
    where [itex]x_1=\frac{2Yl-6Plmg}{3Y}-\frac{l}{3}[/itex]
    After that I get into big muddle as they don't equal to 0
    thanks.
     
  2. jcsd
  3. Oct 19, 2009 #2
    anyone please?
     
  4. Oct 19, 2009 #3

    Redbelly98

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    Energy is not conserved here, because of the friction. However, the energy will decrease by an amount equal to the work done by friction.
     
  5. Oct 20, 2009 #4
    I forgot about friction thanks..
     
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