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Exam question t/f

  1. Sep 13, 2012 #1
    1. The problem statement, all variables and given/known data

    So I took my calc 3 exam today and had this question

    true or false

    magnitude ( v+v) = 2*magnitude( v)

    I put true.

    Thoughts?


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 13, 2012 #2

    LCKurtz

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    You got it correct. Were you just guessing?
     
  4. Sep 13, 2012 #3
    No I did a problem where I had to solve for K in the magnitude give the value of v. Pretty much I took k from the magnitude and solved for it. So I was hoping the same thing applied here.
     
  5. Sep 13, 2012 #4
    Really? I don't see how this is correct.
     
  6. Sep 13, 2012 #5

    LCKurtz

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    If ##\vec v = \langle a,b,c\rangle## what do you get for ##|\vec v|## and ##|2\vec v|##?
     
  7. Sep 13, 2012 #6
    Sorry, of course it's correct.

    I was having a senile moment when I was imagining the two vectors weren't the same! D'oh! :redface:
     
  8. Sep 13, 2012 #7

    LCKurtz

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    Don't feel to bad about that. My first reaction was the same because I was expecting the question to read u+v since, in my opinion, that would have been a better question. Only after I started my reply did I realize the OP had v+v.
     
  9. Sep 13, 2012 #8

    vela

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    Did the same thing here. :smile:
     
  10. Sep 13, 2012 #9
    I obviously need to learn to read twice before posting. Something which you two are obviously better at than me! :smile:
     
  11. Sep 13, 2012 #10

    Mark44

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    If v happened to be perpendicular to itself, the original statement wouldn't be true.:tongue:

    (The zero vector not included, of course.)
     
  12. Sep 13, 2012 #11
    Now you've lost me!
     
  13. Sep 13, 2012 #12

    Mark44

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    Math humor...

    A nonzero vector can't be perpendicular to itself.
     
  14. Sep 13, 2012 #13

    LCKurtz

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    What if it's bent?
     
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