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Spring mechanics question easy

  1. Dec 11, 2009 #1
    1. The problem statement, all variables and given/known data

    A block of mass m1 = 8 kg hangs from the ceiling on an ideal, massless spring with spring constant k = 65 N/m. With the block hanging on the spring, the total length of the spring is L = 3.5 m. When a second block with an identical mass of m2 = 8 kg is tied to the first with a massless string, the spring stretches an additional h0 = 1.5 m.

    The string is cut so that mass m2 falls away. What is the maximum velocity of mass m1?

    3. The attempt at a solution
    [tex] \frac{kx^2}{2}=\frac{mv^2}{2} [/tex]
    x=1.5 and solving for v gives 4.3
    but the answer is 3.42?
  2. jcsd
  3. Dec 12, 2009 #2


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    Science Advisor
    Homework Helper

    Hi ronaldor9! :smile:
    1.5 isn't x …

    you have to (find and) add on the bit of x that's already in the 3.5. :wink:
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