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Homework Help: Elastic energy, spring equation. Help?

  1. Feb 14, 2012 #1
    1. The problem statement, all variables and given/known data
    A 293g block is placed on a spring with a spring constant of 161N/m, compressing it 42cm. What height does the block reach when it is launched?


    2. Relevant equations
    Eel=1/2*k*x2
    Eg=mgh

    3. The attempt at a solution
    Eg=.293*10*.42=1.2306

    1.2306=1/2*161*x2
    1.2306=80.5x2
    .0153=x2
    .1236=x

    Did I make any mistakes? Because I cant get it right.

    ------------------------------------------------------------------------
    nevermind i got it..
     
    Last edited: Feb 14, 2012
  2. jcsd
  3. Feb 15, 2012 #2
    Hi mrphobio,
    You're using the equations the wrong way round.
    The energy stored in the spring (0.5kx2) with spring constant k and compression of the spring x.

    Since energy can't be destroyed, it is transformed into kinetic energy, and finally into potential energy (mgh) with mass m and height of the object h.

    Hope this helps.
     
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