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Homework Help: Conservation of a mechanical energy question

  1. Jul 12, 2004 #1
    Hi, this is my first time here and Id like to thank in advance for any help offered :smile:
    Im having trouble with the following question about 2 masses in an atwoods machine.

    2 masses are initially at rest at the same height, if m2 has a given initial upward speed, how high does m2 rise above its initial position before momentarily coming to rest, (masses for each are given with m2 being heavier)

    I know that I need to show some work before I should post this, but I embarrased to say I dont know how to even apporach it :frown:

    any tips will be greatly appreciated :biggrin:
  2. jcsd
  3. Jul 12, 2004 #2


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    Welcome to PF!
    This is a conservation of mechanical energy question.
    Set up the initial mechanical energy of the whole system (kinetic+potential)
    When the system falls momentarily at rest (assuming that the string remains taut all the time), the system only have potential energy.
    As a hint, note that with a taut, inextensible string, the increase of height for m2 must equal the decrease of height for m1
    Last edited: Jul 12, 2004
  4. Jul 12, 2004 #3
    First, find the acceleration of the masses. Then use some kinematics to find the distance. Should be dead easy.
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