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Homework Help: Hooke's Law Question

  1. Oct 7, 2007 #1
    1. The problem statement, all variables and given/known data
    During spring semester at MIT, residents of the parallel buildings of the East Campus dorms battle one another with large catapults that are made with surgical hose mounted on a window frame. A balloon filled with dyed water is placed in a pouch attached to the hose, which is then stretched through the width of the room. Assume that the stretching of the hose obeys Hooke's law with a spring constant of 110 N/m. If the hose is stretched by 5.90 m and then released, how much work does the force from the hose do on the balloon in the pouch by the time the hose reaches its relaxed length?

    2. Relevant equations
    F=-kx W=Fd

    3. The attempt at a solution
    I tried this problem and got -649 as the answer for the force, however I feel as if it is not correct, I also don't know what to do to get work, do I just multiply the -649 by 5.9 again to get work? Am I doing something wrong?
  2. jcsd
  3. Oct 7, 2007 #2


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    Staff Emeritus
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    Gold Member

    Start by calculating the elastic potential energy stored in the streched pouch/hose.
  4. Oct 7, 2007 #3
    Okay, I did that and got 1914.55 as my answer, is that my answer? It seems as if I use Ws=-1/2kx^2 the negative (-1914.55) would be my answer and work? Am I right?
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