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Spaceships? problem help

  1. Nov 12, 2007 #1
    1. The problem statement, all variables and given/known data

    Problem Statement: Astronaut Pam Melroy, history's 3rd woman space shuttle pilot, flew the space shuttle discovery to the International Space Station to complete construction in October of 2000. To undock from the space station, Pilot Melroy released goooks holding the 2 spacecraft together and the 68 000-kg shuttle pushed away from the space station with the aid of 4 large springs.
    A) if the 73 000-kg space station moved back at a speed of 0.50 m/s, how fast and in what direction did the space shuttle move?
    B) What was the relative speed of the 2 spacecraft as they separated?

    [tex]M_{1}[/tex]= 68 000-kg
    [tex]V_{1F}[/tex]= ?
    [tex]M_{2}[/tex]= 73 000-kg
    [tex]V_{2F}[/tex]= -0.50 m/s
    [tex]V_{o}[/tex]= 0 m/s

    2. Relevant equations

    ([tex]M_{1}[/tex] + [tex]M_{2}[/tex]) [tex]V_{o}[/tex] = [tex]M_{1}[/tex][tex]V_{1F}[/tex] + [tex]M_{2}[/tex][tex]V_{2F}[/tex]

    3. The attempt at a solution

    (68 000-kg + 73 000-kg)0 m/s = ((68 000-kg)( [tex]V_{1F}[/tex] ) + (73 000-kg)(-0.50 m/s)

    0 = (68 000-kg)[tex]V_{1F}[/tex] - 36 500-kg [tex]\times[/tex]m/s
    add -36 500-kg [tex]\times[/tex]m/s to 0

    36 500-kg [tex]\times[/tex]m/s = (68 000-kg)[tex]V_{1F}[/tex]

    = 0.53676 m/s

    BUT the back of the book for this odd says
    1.04 m/s
  2. jcsd
  3. Nov 12, 2007 #2
    needs help very very very fast
  4. Nov 12, 2007 #3


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    Science Advisor
    Homework Helper

    It is asking you the speed they separate, remember that the ISS is also moving so it is the total speed between them.
    You have worked out the speed of the shuttle from the starting point.
  5. Nov 12, 2007 #4
    so my answer is the initial velocity??
  6. Nov 12, 2007 #5


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    Science Advisor
    Homework Helper

    No the answer is 0.5m/s for the iss plus 0.53676 m/s for the shuttle
    So the velocity they are moving apart is 0.5 + 0.53676 = 1.04m/s
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