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Homework Help: Block/Spring Problem (Kinetic Energy)

  1. Mar 9, 2010 #1
    1. The problem statement, all variables and given/known data

    A 13 kg block on a horizontal surface is attached to a horizontal spring of spring constant k = 4.3 kN/m. The block is pulled to the right so that the spring is stretched 13 cm beyond its relaxed length, and the block is then released from rest. The frictional force between the sliding block and the surface has a magnitude of 100 N.

    (a) What is the kinetic energy of the block when it has moved 4.8 cm from its point of release?

    (b) What is the kinetic energy of the block when it first slides back through the point at which the spring is relaxed?

    (c) What is the maximum kinetic energy attained by the block as it slides from its point of release to the point at which the spring is relaxed?f

    2. Relevant equations

    ElasticPotentialEnergy= 1/2ky^2

    3. The attempt at a solution

    I honestly don't know where to begin. I used the numbers I was given to find the elastic potential energy at the beginning and came up with 36.34 J... and now I am not sure what to do.

    Us= (1/2)(4300N/m)(.13)^2
    Us= (36.34J)
  2. jcsd
  3. Mar 9, 2010 #2


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    Homework Helper

    Use the conservation of energy, remembering to account for the energy lost by friction.
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