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Homework Help: Finding the Compression of a Spring Using the Work-Energy Theorem

  1. Apr 13, 2013 #1
    1. The problem statement, all variables and given/known data

    A 6.0kg box moving at 3.0m/s on a horizontal, frictionless surface runs into a light spring of force constant 75 N/cm. Use the work-energy theorem to find the maximum compression in the spring.

    2. Relevant equations

    W = K2 - K1

    W = (1/2)*m*v^2 - (1/2)*m*vo^2

    W = - (1/2)*k*x^2

    3. The attempt at a solution

    - (1/2)*k*x^2 = 0 - (1/2)*m*vo^2, where k = 75000N/m

    x = ((m*v^2)/k)^(1/2) = ((6.0kg*(3m/s)^2)/75000N/m)^(1/2)

    x = 0.027m

    But the answer in the book is x = 0.085m. I just can't see what I am doing wrong unless my textbook is wrong.
  2. jcsd
  3. Apr 13, 2013 #2
    Recheck your value for k.
  4. Apr 14, 2013 #3
    Oh my god, thanks!
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