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Multiple Answers stored in matrix?

  1. Jul 23, 2011 #1
    If
    KE=(m V^2)/2
    Then
    V=matrix([[(2^(1/2)*KE^(1/2))/m^(1/2)], [-(2^(1/2)*KE^(1/2))/m^(1/2)]])
    Would this notation be considered improper?
    I'm just wondering because this is what my computer printed out.
    or something like this
    V=matrix([-5],[5]) m/s
    Is this acceptable?
     
  2. jcsd
  3. Jul 23, 2011 #2

    SammyS

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    Solve the equation, KE=(m V2)/2, for V, using algebra. You should get two solutions. That's all your calculator is telling you.

    Now, is V velocity or is it speed, in your equation?
     
  4. Jul 23, 2011 #3
    Ya I'm completely aware that there are two solutions and that V is a vector velocity. I'm just asking if this is proper notation and if it's ok for me to leave my results like this, that is all. I don't see why it would not be ok for me to leave my results like this. I just have never seen anyone set solutions equal to a matrix if there are multiple solutions and don't know how it would be received by my professors if I leave my results like this. I don't don't see why not, but I just wanted to make sure.
     
  5. Jul 23, 2011 #4

    SammyS

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    How would you write the solution if you did it by hand?
     
  6. Jul 23, 2011 #5
    Not given any context on the problem I can't determine the direction of the velocity. So I would write it like

    V = +/- 5 m/s

    but I guess if there were more than two solutions, in this case there wouldn't be, but like if I was solving a equation and get something like
    x=4
    x=5
    x=6
    I would write it like
    x=4,5,6
     
  7. Jul 23, 2011 #6

    SammyS

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    So, I would write my answer like either of those, not as a matrix.
     
  8. Jul 23, 2011 #7
    Ya I would to. That's why I question if it's proper or not to leave my answers like this. Given that there can only be one answer in a certain situation and your given multiple I feel as if it's improper to write
    x= 4 or 5 or 6
    to indicate that it can only be one of those solutions
    that's why I think this would be better to write it like this if they represent the same things
    x=[4 5 6]
    not sure if it would be understood as representing the same things
    like could someone say that doing so is incorrect or wrong because
    x= 4 or 5 or 6
    implies something different than
    x=[4 5 6]
    ?
     
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