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Homework Help: Momentum and its Conservation

  1. Jul 12, 2010 #1
    1. The problem statement, all variables and given/known data

    Astronaut Jane's lifeline to her spaceship comes loose and she finds herself stranded, "floating" 75.0m from the spaceship. She throws her 2.00kg wrench at 20.0m/s in a direction away from the ship. If she and her spacesuit have a combined mass of 175kg how long does it take her to coast back to the spaceship?

    2. Relevant equations

    3. The attempt at a solution

    This one I am so lost about...

    Do I use the equation: (Mass of Suit x Mass of Jane) Initial Velocity + Mass of wrench (Initial Velocity) = (M of Suit + M of Jane) (V 1 + M of wrench (V 1 of wrench)

    Therefore = (175kg) 0 + 2kg (0) = (175kg) (final velocity + 2kg (20.0m/s)
  2. jcsd
  3. Jul 12, 2010 #2
    All is good to this point.
  4. Jul 12, 2010 #3
    Do I have to factor in the fact that she floated 75 m away?
  5. Jul 12, 2010 #4
    That does not influence conservation of momentum.

    You only need the distance to find the time it takes to get back to the ship.
  6. Jul 12, 2010 #5
    then 0=175(final velocity) + 40

    final velocity = -40/175
    = -0.23 m/s ??
  7. Jul 13, 2010 #6


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    Looks okay so far.
  8. Jul 13, 2010 #7
    what else needs to be done???
  9. Jul 13, 2010 #8


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    You need to find out how much time it takes for someone to travel 75.0 m when traveling at a speed of 0.229 m/s.
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