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Homework Help: Elastic Potential Energy of a glider

  1. Sep 4, 2007 #1
    1. The problem statement, all variables and given/known data
    A glider with mass 0.200kg sits on a frictionless horizontal air track, connected to a spring with force constant k = 5.00N/m. You pull on the glider, stretching the spring 0.100m and then release it with no initial velocity. The air track is turned off, so there is a kinetic friction force acting on the glider. What must be the coefficient of kinetic friction uk between the air track and the glider so that the glider reaches x = 0 position with zero speed.

    2. Relevant equations
    U = 1/2kx^2

    3. The attempt at a solution
    U1 + U2 = K1 + K2
    0 + 1/2(kx^2) + Wother = 0 + 0
    -1/2(5.00N/m)(.100m)^2 = Ff (0.100m)
    -1/2(5.00N/m)(.100m) = Ff
    Ff = -0.25N

    uk = 0.25N / (0.200kg*9.8m/s^2)
    uk = 0.128
    Last edited: Sep 4, 2007
  2. jcsd
  3. Sep 4, 2007 #2


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    Homework Helper

    Yes, that looks right to me... for the beginning I'd write something like:

    Wother = Mech.energy_final - Mech.energy_initial

    Wother = (U2 + K2) - (U1 + K1)

    (where K represents kinetic energy, and U represents elastic potential energy)
  4. Sep 4, 2007 #3
    thank you
  5. Sep 4, 2007 #4


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    Homework Helper

    no prob.
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