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Really though relative motion/momentum question

  1. Oct 12, 2005 #1

    404

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    Okay, really tough for me atleast.
    Answers are 1.15 m/s and 0.346 m/s
    edit: title = tough*
     
  2. jcsd
  3. Oct 12, 2005 #2

    HallsofIvy

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    Staff Emeritus
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    Conservation of momentum. Or that the center of mass of the girl-plank system must remain stationary since there is no outside force on the system.

    Be careful with speeds. If the plank's speed, relative to the ice is v, then the girl's speed relative to the ice is (1.5+ v) m/s (of course, the plank moves opposite to the girl so v will be negative). The girl's momentum, then, is
    45(1.5+ v) kgm/s and the plank's is 150 v kgm/s. By conservation of momentum, 45(1.5+ v)+ 150v= 0.
     
  4. Oct 12, 2005 #3

    404

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    Got it... Thanks!
     
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