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Vectors addition

  1. Dec 14, 2014 #1
    1. The problem statement, all variables and given/known data
    A plane flies the following paths: 168 km to the Northeast, 144 km to the Southeast, 246 km to the Southwest, and then 127 km to the Northwest. At the end of the trip, how far was the plane from the original airport?

    2. Relevant equations Pythagorean theorem, trigonometry


    3. The attempt at a solution I tried to add the vectors up and use that as an answer but it didnt work, I also tried to make a triangle out of it to use one of the equation but i couldnt seem to get anywhere
     
  2. jcsd
  3. Dec 14, 2014 #2

    Orodruin

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    Please show us your attempt. Just stating in words what you tried and that it did not work is not getting us very far. We will be able to be of much more help if you actually show us what you tried.
     
  4. Dec 14, 2014 #3
    168-144-246+127=-95
     
  5. Dec 14, 2014 #4

    jedishrfu

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    You need to show your work for this. Saying it didn't work means there's something wrong with your calculations and we could help you find the mistake.

    Anyway, have you tried to draw a picture and then match your picture to your calculations. You might discover your mistake that way.
     
  6. Dec 14, 2014 #5
    yeah i drew a picture but it ended up looking like a rectangle. and my work is posted in the post right above yours
     
  7. Dec 14, 2014 #6

    jedishrfu

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    Right off the bat it looks like you just added the magnitudes. What happened to the angles where the plane travels northeast ... ?

    Vectors have magnitude and direction which you must consider when adding them together.
     
  8. Dec 14, 2014 #7
    it does not say what the angle measurements are though
     
  9. Dec 14, 2014 #8

    Orodruin

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    It does say what directions the displacements are in. I suggest you go back to your drawn picture, it should look like four lines which are pair-wise parallel. If it helps, I suggest using a coordinate system where south east is the direction of positive x coordinate and north east that of positive y coordinate.
     
  10. Dec 14, 2014 #9
    i have drawn a bunch of different ways, and it still makes no sense because none of the lines were parallel. i am completely stuck right now on this question
     
  11. Dec 14, 2014 #10

    Orodruin

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    Then you did not draw it correctly. A line going south east is definitely parallel to one going north west.
     
  12. Dec 14, 2014 #11

    jedishrfu

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    Why not post your drawing?

    If the plane travels northeast that means it travel x miles east and y miles north so now you'd have it in coordinates that you can add correctly namely north as positive added to south as negative and east as positive and west as negative.
     
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