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Homework Help: Horizontal spring with friction

  1. Feb 4, 2013 #1
    1. The problem statement, all variables and given/known data
    A spring with negligible mass has a constant of 105 N/m. It has been compressed horizantally with a 2 kg mass for a distance of 0.1m. If the mass has moved after release for a distance of 0.25m, what is the coefficient of kinetic friction between mass and horizontal surface.

    2. Relevant equations
    F=-kx (spring force)
    f= C N, f is friction, C is the kinetic friction coefficient, and N is the force exerted on the mass by the horizontal surface

    3. The attempt at a solution
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 4, 2013 #2
    i would recommend using work to solve this problem.
    also work done by a spring is .5*k*x^2
  4. Feb 4, 2013 #3
    Conservation of energy would be the easiest way to solve this.
    What happens to the potential energy initially stored in the spring?
  5. Feb 4, 2013 #4
    ok the work done by the spring is 0.5*k*x02 - 0.5*k*x12
    we know that x0=-0.1m
    but what is x1, since the 0.25m given in the question is the distance not the displacement??!?
  6. Feb 4, 2013 #5
    ok i see what you mean ap123
    the energy stored initially = the work done by the friction force
    0.5*k*x0^2= C * mg * distance
  7. Feb 4, 2013 #6
    Yes, you've got it :)
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