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Homework Help: Physics 11 help please?

  1. Dec 18, 2008 #1
    1. The problem statement, all variables and given/known data

    A spring can be compressed 12 cm by an applied force of 6.0 N. A 2.8 kg box sliding along a frictionless surface approaches this spring at a speed of 1.9 m/s. How far will the spring be compressed when the box comes to a stop?

    2. Relevant equations

    Ep = 0.5kx2

    0.5mv2 = 0.5kx2
    3. The attempt at a solution

    I worked out that k = 50 N/m
    0.5mv2 = 0.5kx2
    0= 25x2

    but this doesn't work out because x should be 0.45 m. help?
  2. jcsd
  3. Dec 18, 2008 #2


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    Homework Helper

    When the box comes to a stop all of the Kinetic Energy will be converted to the potential energy of the spring.

    Use the formula you had only put the initial KE of the box in before it touches the spring.

    And all will be well.
  4. Dec 18, 2008 #3
    great thanks !
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