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Homework Help: Conservation of Momentum of astronaut

  1. Apr 10, 2008 #1
    1. The problem statement, all variables and given/known data
    An astronaut is a distance [tex]L[/tex] from her spaceship, and is at rest with respect to the ship, when she discovers that her tether has broken. She tosses a wrench with a speed of [tex]V_W[/tex] in the opposite direction of the ship to propel herself back to the ship. The astronaut has mass [tex]M_A[/tex], and the wrench has mass [tex]M_W[/tex].

    How long does it take her to reach the ship in terms of [tex]L[/tex], [tex]M_A[/tex], [tex]M_W[/tex] and [tex]V_W[/tex]?

    2. Relevant equations

    Conservation of momentum: [tex]P_i=P_f[/tex]
    I don't know what equation to use to find time? [tex]v= d/t[/tex]?

    3. The attempt at a solution
    [tex](M_A+M_W)(V_i)=(M_W)(V_Wf)-(M_A)(V_Af)[/tex]
    [tex]V_Af=(M_f)(V_Wf)/(M_A)[/tex]

    [tex]t=d/v[/tex]
    [tex]t=(L)(M_A)/(M_W)(V_Wf)[/tex]

    Is that right? Thanks.
     
    Last edited: Apr 10, 2008
  2. jcsd
  3. Apr 10, 2008 #2
    Seems correct to me.
     
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