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Homework Help: Conservation of energy

  1. Jul 11, 2012 #1
    1. The problem statement, all variables and given/known data
    i attached the problem since its easier.

    2. Relevant equations

    im not sure. i know the equation for h has to be included. but im not sure what other equations must be used.

    3. The attempt at a solution

    I honestly dont know how to begin. Any kind of help would be greatly appreciated!

    Attached Files:

  2. jcsd
  3. Jul 11, 2012 #2


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  4. Jul 11, 2012 #3
    i didnt think i had to use the potential spring energy equation because i need to find the velocity for when it comes back down....im really bad at this lol sorry
  5. Jul 11, 2012 #4
    The terminology in the problem statement is confusing. When the problem refers to "strength", what it is really referring to is stiffness or spring constant. The term strength is usually reserved for when something breaks. You also apparently need to assume that the force the bow string exerts on the arrow is directly proportional to the draw displacement, such that when the draw displacement is zero, the force is zero, and when the displacement is d, the force is kd. So...., during the time that the arrow is in contact with the bow, what is the average force exerted on it by the bow? How much work is done on the arrow by the bow during the contact period? What does this translate into in terms of gravitational potential energy when the arrow reaches its maximum height. What is the upward velocity of the arrow when it reaches its maximum height?
  6. Jul 11, 2012 #5
    would the equation be 1/2mv2=mgh

    then replace h with the equation for h and isolate v??

    im just not understanding this problem.
    Last edited: Jul 11, 2012
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