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Vector Problem - is this even solvable?

  1. Sep 10, 2011 #1
    1. The problem statement, all variables and given/known data
    [PLAIN]http://img703.imageshack.us/img703/8599/physicsks.png [Broken]


    2. Relevant equations
    I'm considering cross product and dot product rules, yet I don't know where to begin with this one.


    3. The attempt at a solution
    I have two pages of scratch paper that is littered with failed attempts to solve the problem.

    -There are no values for a or b given.
    -Is there even enough information to solve these problems?
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Sep 10, 2011 #2

    wukunlin

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    this is basically a set of 2X2 simultaneous equation, which you can do by seperating the two components of each vector
     
  4. Sep 10, 2011 #3

    SteamKing

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    Hint: a and b are constants which multiply the vectors A and B, respectively. There is no implied dot or cross product in the problem statement as shown.
     
  5. Sep 10, 2011 #4
    I think I'm on the right track... thanks guys. Can you confirm if this is heading in the correct direction?

    a<81,-73>+b<-79,49>+<60,85>=<0,0>

    So,

    81a-79b+60=0
    -73a+49b+85=0

    ?
     
  6. Sep 10, 2011 #5

    wukunlin

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    yup :)
     
  7. Sep 10, 2011 #6
    These numbers are ugly... mind sticking around until I work it out? :)
     
  8. Sep 10, 2011 #7
    Still haven't figured it out :/
     
    Last edited: Sep 10, 2011
  9. Sep 10, 2011 #8

    wukunlin

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    do you have to solve it by hand? or are you allowed to use calculators/computers?
     
  10. Sep 10, 2011 #9
    Even if I solve it, I still think there's something going wrong... I'll use a computer. I just tried doing it with matrices, lol.
     
  11. Sep 10, 2011 #10

    wukunlin

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    you can always substitute your answers back into the question and see if the identity holds, faster and simpler than rechecking all your steps
     
  12. Sep 10, 2011 #11
    You're right - I have new values for a and b

    a=5.520297
    b=6.489422

    Pretty sure I got it! Thank you for your help!
     
  13. Sep 10, 2011 #12

    wukunlin

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    glad to help :)
     
  14. Sep 10, 2011 #13
    It was correct - my online homework thing accepted it, lol. The algebra was just a little ambiguous.
     
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