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Homework Help: Momentum of Astronaut and Satellite

  1. Oct 25, 2011 #1
    1. The problem statement, all variables and given/known data
    A 92-kg astronaut and a 1200-kg satellite are at rest relative to the space shuttle. The astronaut pushes on the satellite, giving it a speed of 0.14 m/s directly away from the shuttle. Seven-and-a-half seconds later the astronaut comes into contact with the shuttle. What was the initial distance from the shuttle to the astronaut?


    2. Relevant equations
    (m1)(v1) = (m2)(v2)


    3. The attempt at a solution
    (1200)(14)=(92)(v2)

    (v2)=182.61

    d= vt

    d=182.61*7

    d=1278.26 m (Is this right?)
     
  2. jcsd
  3. Oct 25, 2011 #2

    DaveC426913

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    What does your gut tell you about that answer? How far is that?

    Does that seem right - considering the velocity and time involved?

    If no, go back and check all your numbers.
    And your decimals.
     
    Last edited: Oct 25, 2011
  4. Oct 25, 2011 #3
    Oh, wow, another careless mistake like on my previous question...So, besides the "decimal manipulation", are there any other errors like lack of vectors (negative and positive). I am having a dilemma on whether to make v1 negative since it's going the opposite direction.
     
  5. Oct 25, 2011 #4

    DaveC426913

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    There's also a delta-t issue.

    As for neg and psotive, I suppose it depends on how rigorous you need your work to be. If you just need to supply the value, it'll work out.
     
  6. Oct 25, 2011 #5
    I guess I just need the scaler quantity. Thanks for notcing my Δt error also. I need to read the questions more carefully.

    By the way, I got my answer to be 13.725 meters if someone can confirm.
     
  7. Oct 25, 2011 #6

    DaveC426913

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    Hm. I get 13.7 - and that's rounded up from 13.695.

    Ah. I see. Sig digs.
    I did 1.826*7.5.
    You did 1.83*7.5 = 13.725.

    Well, it still rounds to 13.7.
     
  8. Oct 25, 2011 #7
    It's just my lazy rounding error. Thanks for the confirmation!
     
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