1. Not finding help here? Sign up for a free 30min 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!

Angle of Vector

  1. Sep 14, 2010 #1
    1. The problem statement, all variables and given/known data
    car travels 18.2km due north then 43.2km at 53 degrees west of north. Find magnitude of car's resultant displacement.

    b.) calculate the direction of the car's resultant displacement, measured counter-clockwise from the northerly direction.


    2. Relevant equations



    3. The attempt at a solution
    Ax = 18.2sin(90) =18.2 Ay = 18.2cos(90) = 0
    Bx = 43.2sin(143) = 26 By = 43.2cos(143) = -34.501
    Cx = 44.2 Cy = -34.501

    44.2^2 + -34.501^2 = 3143.82, square root of that = 56.07

    arctan(-34.504/44.2) = -37.98 degrees

    so part b says counter-clockwise from north, so wouldn't it be from 90 degrees so should the angle be 127.98? I entered that as an asnwer and it's wrong so not sure what I did wrong.
     
    Last edited: Sep 14, 2010
  2. jcsd
  3. Sep 14, 2010 #2
    when you did Bx and By, where did you get 43.2 and 143 degrees?
     
  4. Sep 14, 2010 #3
    typo, it was due north 43.2km not 432, the 143 degrees is when it says 53 degrees west of north, north is 90, so 90 + 53 = 143. I already got that part right, I just don't understand the wording on part b.
     
  5. Sep 14, 2010 #4
    recheck your math for Bx and By. Bx should be 260 and By should be -345. Also, you're using the Pythagorean theorem when you should be using law of cosines. the angle across from the resultant vector should be 90 + (90 - 53) = 127. In other words, it's 53 degrees from the vertical not the horizontal.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Angle of Vector
  1. Vector angle (Replies: 12)

  2. Vector Angles (Replies: 3)

  3. Angle of a Vector (Replies: 4)

  4. Angle of vector (Replies: 4)

  5. Angle of Vector (Replies: 7)

Loading...