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!

Vector Magnitude and Direction Problem

  1. Sep 30, 2009 #1
    1. The problem statement, all variables and given/known data
    Vector has a magnitude of 5.4 m and is directed east. Vector has a magnitude of 3.5 m and is directed 36° west of north. What are (a) the magnitude and (b) the direction (from east) of a + b? What are (c) the magnitude and (d) the direction (from east) of b - a ? Round your angles to the nearest degree.


    3. The attempt at a solution

    this is what i have attempted so far.
    a) ax = 5.4m - 3.5sin36
    = 3.34 m
    bx = 3.5sin36
    = 2.83 m
    A = sqrt(3.34^2 + 2.83^2)
    = 4.38 m
    b) theta = arctan(2.83/3.34)
    = 40.27 deg

    c) ax = 5.4m + 3.5sin36
    = 7.46 m
    bx = 3.5sin36
    = 2.83 m
    A = sqrt(7.46^2 + 2.83^2)
    = 7.98 m
    d) STUCK.
    arctan(2.83/7.46) = 20.79

    I am using WileyPlus program, so they are able to detect if my answer is right or wrong. so far i have attempted these answers, and they accepted it EXCEPT the part D. i don't get what i did wrong.

    thanks for the help
     
  2. jcsd
  3. Sep 30, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    If you measure the angle in clockwise direction, it should be taken as negative.
     
  4. Sep 30, 2009 #3
    thanks for the reply!

    i did the negative also. i input -20.79 and they wont accept it.
     
  5. Sep 30, 2009 #4

    rl.bhat

    User Avatar
    Homework Helper

    They have asked the direction of (b - a), which lies in the second quadrant.
     
  6. Sep 30, 2009 #5
    thanks dude you hit the spot right there!

    appreciated it! now i can sleep well.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Vector Magnitude and Direction Problem
Loading...