1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Adding the vectors ijk notation

  1. Feb 17, 2013 #1
    1. The problem statement, all variables and given/known data
    Add the following 3 displacement vectors and give the answer in ijk notation and in magnitude and direction format.
    A = 3i - 3j m
    B = i - 4j m
    C = -2i + 5j m.

    Then I have to do a scetch of the resultant vector...which i'll call D.


    2. Relevant equations



    3. The attempt at a solution
    So I know to get vector D's i hat and j hat components...i just add the i's and j's of the vectors that make it up so

    i = 3 + 1 - 2 = 2
    j = -3 - 4 + 5 = -2

    right?

    so then to find the magnitude of D i do

    √(2)² + (-2)²

    which comes out to √8 which is roughly 2.83 m here

    Then to find the angle i do the inverse tan of (-2/2) or -1....which comes out to -45°

    Now to graph....should I find the magnitude and angle of each vector?

    A = √(3)² + (-3)² = √18 = 4.24 m at -45°
    B = √(1)² + (-4)² = √17 = 4.12 m at -76°
    C= √(-2)² + (5)² = √29 = 5.39 m at -68°

    Do I graph them just like this? Because how can the resultant vector be at the SAME angle at vector A? It would be a smaller version of vector A because the magnitude of A is >D and the angle is the same.

    Can anyone point out where I'm misunderstanding this?
     
  2. jcsd
  3. Feb 17, 2013 #2
    The angle of the resultant vector is not 45°. In which quadrant of the XY plane is it?

    The problem with arctan is that it confuses (-a)/b with a/(-b), and (-a)/(-b) with a/b. So you have to keep an eye on the signs to determine which quadrant it is, and what the angle really is.
     
  4. Feb 17, 2013 #3
    You don't need to work out the magnitude and angle of the vectors.
    For example, for A = (3i - 3j) m, the x-component is 3m and the y-component is -3m.
    So, just draw a line from the origin to the point (3m, -3m)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Adding the vectors ijk notation
  1. Adding vectors (Replies: 4)

  2. Adding Vectors (Replies: 1)

  3. Adding Vectors (Replies: 3)

  4. Adding Vectors (Replies: 1)

Loading...