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!

Homework Help: How do you find the direction of a vector given its magnitude and angle?

  1. Sep 4, 2009 #1
    1. The problem statement, all variables and given/known data

    Vector A points in the negative x direction. Vector B points at an angle of 33.0 degrees above the positive x axis. Vector C has a magnitude of 13 m and points in a direction 37.0 degrees below the positive x axis.

    Given that , Vector A + Vector B + Vector C = 0, find the magnitudes of Vector A and Vector B.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 4, 2009 #2
    Construct a vector diagram. You should get a closed triangular loop from the three vectors.
  4. Sep 4, 2009 #3


    Staff: Mentor

    Let a = the magnitude of A = |A|
    Let b = |B|
    Let c = |C| = 13 (given)

    Write the three vectors in terms of their coordinates, like this:
    A = -a*i + 0*j
    B = b*cos(33 deg)*i + b*sin(33 deg)*j
    C = 13*cos (-37 deg)*i + 13*sin(-37 deg)*j

    For the three vectors to sum to zero, their horizontal components have to add to zero, and their vertical components have to add to zero. Set up these two equations and solve for the unknowns a and b. Once you have these values you can find the magnitudes of A and B.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook