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Homework Help: Questions About VECTORS.

  1. Sep 29, 2008 #1
    The problem statement, all variables and given/known data
    A) Vector A = 7.00 m and points 40.0o north of east. Vector B = 1.90 m and points 15.0o west of north, and Vector C = 2.10 m and points 15.0o west of south.
    What is the magnitude of the resultant vector A+B+C?

    B) What angle does the resultant vector A+B+C make with respect to the east?


    The attempt at a solution
    f9qcee.jpg
    I know, you wish I hadn't tried. ahaha.

    Link incase the above doesn't show up:
    http://i36.tinypic.com/f9qcee.jpg

    Annnd I also got 5.35 m & 83.2 deg at some point.

    Thanks,
    KP.
     
  2. jcsd
  3. Sep 29, 2008 #2

    LowlyPion

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    Homework Helper

    Welcome to PF.

    Nice picture.

    Apparently you understand that the sum of the Vectors can be represented as the sum of the components in x and y.

    Unfortunately the y component of your B vector is calculated incorrectly (how can a vector of 1.9 have a 3.37 component?), dooming your effort to get the right answer.
     
  4. Sep 29, 2008 #3
    woww. silly mistake. forgot to sq rt it. haha. pretend it says 1.84 :). where do i go from there?
    Would this be correct?
    Sum of y = Ay+By+Cy
    Sum of x = Ax+Bx+Cx
    ?
    And then use sin/cos/tan to get the angle?
     
  5. Sep 29, 2008 #4

    LowlyPion

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    OK. Let's pretend too that you know that the resulting vector is the scalar addition of the x components and the scalar addition of the y components.

    Add up all the x's.
    Add up all the y's.

    Express that as a vector with magnitude - doing that Pythagoras thing you do and figure the angle from the arctan in degrees and then get credit for a right answer.
     
  6. Sep 29, 2008 #5
    I got it! Thank you thank you! :) Guess I just needed a second set of eyes.
     
  7. Sep 29, 2008 #6

    LowlyPion

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    Homework Helper

    Cheers and good luck then.

    No more math errors now.
     
  8. Sep 29, 2008 #7
    Haha no promises, but I will double check my calculations in the future (even the really simple ones). :)
     
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