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Homework Help: Circular Motion: Change in Height, Box Struck by Arrow

  1. Feb 29, 2008 #1
    1. The problem statement, all variables and given/known data

    A box of mass 4.750Kg is suspended from a rope which is attached to the ceiling and is currently at rest. You then shoot an arrow horizontally with a velocity of 21.00 m/s toward the box while standing 4.5m away from it. You may neglect air resistance.

    A. With what velocity will the arow strike the box?
    B. If the arrow has a mass of 0.2500Kg, what is the max change in height the box theoretically will experience?

    2. Relevant equations

    b = Box, a = arrow

    KEib + KEfb = KEia + KEfa

    Fc = MV^2/r

    Fg = mg

    3. The attempt at a solution

    So what I did was I first solved for the Final Velocity of the box which would become the new initial velocity after the arrow struck the box using the KEib + KEfb = KEia + KEfa.

    0.5(4.750)V^2 = 0.5(0.25)(21.00)^2

    Solving for the Velocity, I got 4.82m/s. so that becomes the new velocity I have and the New initial velocity would be 0. My New givens are:

    Vi = 4.82m/s
    Vf = 0m/s
    A = -9.81m/s^2
    [tex]\Delta[/tex]y = ?

    If I'm looking for the change in height, I don't feel like I need Centripetal Force. Would I just need to worry about [tex]\Delta[/tex]y? or do I have to use the Centripetal force equation?
    Last edited: Feb 29, 2008
  2. jcsd
  3. Feb 29, 2008 #2
    KEib + KEfb = KEia + KEfa

    and what about PE ??:wink:
  4. Feb 29, 2008 #3
    Oh! Haha I completely forgot. Thanks so much!
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