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!

Calculating resultant

  1. Oct 5, 2011 #1
    Hello, can someone please explain why (B.y) for the y-component is negative for the sin30. thanks .
    question is below.

    [PLAIN]http://img710.imageshack.us/img710/6150/resulant.jpg [Broken]
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 5, 2011 #2
    The y-component for the sin30 is because it's actually sin(-30): the angular displacement is in the opposite direction of the reference positive direction. Intuitively, this makes sense because when you add the vectors in component form you would get a vector whose y-component is greater than the y-component of the 8.00N @ 40degrees vector despite the fact that the vectors shown are traveling in opposite directions from the x-axis, that is, their y-components should have opposite signs.
     
  4. Oct 5, 2011 #3

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Welcome to PF yardy_genius,

    It's just a sign convention. By convention, you're taking "up" to be the positive y-direction and "down" to be the negative y-direction. You could just as easily adopt the opposite sign convention. All that matters is that you pick a convention and stick to it (i.e. use it consistently throughout the problem).
     
  5. Oct 5, 2011 #4
    thanks alot
     
  6. Oct 5, 2011 #5
    thanks , you guys really helped a lot
     
  7. Oct 5, 2011 #6
    No problem; glad I could help. Cepheid's answer is also pretty important, by the way. He touched on a way more critical point than I did, which is that you can use almost any convention that's convenient, so long as you stick to it (and make sure to revert it to the original terms if necessary/requested).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Calculating resultant
Loading...