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Vectors problem, help

  1. Sep 14, 2009 #1
    vectors problem, help plz

    1. The problem statement, all variables and given/known data
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    2. Relevant equations



    3. The attempt at a solution

    I used the pythagorem theorem on the first two vectors and named it vector x. It turned out to be 4.8km and I used vector x plus 3.1km of the other vector. I got 7.9km at 45 degrees NE. The book says it should be 7.8km at 38 degrees NE. What did I do wrong? OR is it the book>
     
  2. jcsd
  3. Sep 14, 2009 #2
    Re: vectors problem, help plz

    Is the resultant vector from 2.6km north and 4.0km east at a 45 degree angle from east?

    If not you can't simply add 4.8km to 3.1km because they wont be in the same direction.
     
  4. Sep 14, 2009 #3

    rl.bhat

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    Re: vectors problem, help plz

    4.8 km and 3.1 km are not in the same line.
    Find the angle between them.
    It is equal to (45 degrees - angle between 4 km and 4.8 km.)
     
  5. Sep 14, 2009 #4
    Re: vectors problem, help plz

    Aren't both lines( vector x and the 3.1km vector both going north east?
     
  6. Sep 14, 2009 #5

    rl.bhat

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    Re: vectors problem, help plz

    No. It is not. Draw the scale diagram and verify.
     
  7. Sep 14, 2009 #6

    ideasrule

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    Re: vectors problem, help plz

    Well, you went north 2.6 km, then east 4 km. To have a 45-degree angle, those two values have to be equal, which they aren't.
     
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