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Homework Help: Work/energy with a spring

  1. Nov 12, 2008 #1
    1. The problem statement, all variables and given/known data
    A (m)kg box moving at (v)m/s on a horizontal, frictionless surface runs into a light spring of force constant (k)N/m.
    Use the work-energy theorem to find the maximum compression of the spring.

    2. Relevant equations
    kinetic energy=1/2 m v^2
    Change in kinetic energy = work done
    hookes law: KS=F
    FS=Work done

    3. The attempt at a solution

    (k)s^2= 0.5 x (m) x (v)^2

    s =[0.5(m)(v)^2 / (k)] ^1/2

    OR if
    1/2 (k)s^2 = Work

    0.5 (k) s^2 = 0.5 x (m) x (v)^2
    s ^2 =0.5(m)(v)^2 / 0.5(k)
    s=[(m)(v)^2 / (k)]^1/2
  2. jcsd
  3. Nov 12, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That's the one you want. The energy stored in a spring is 1/2kx^2, not kx^2.
  4. Nov 12, 2008 #3
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