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 component perpendicular

  1. Sep 8, 2012 #1
    1. The problem statement, all variables and given/known data

    Suppose v = <-3,-2, 1> and w = <-1,1,1>. Then
    projw(v) = < -2/3, 2/3, 2/3 > ,
    and the component of v perpendicular to w is?




    2. Relevant equations



    3. The attempt at a solution

    I understood how to get the projection, and tried using the component formular Compaonb= a*b/magnitude( A )

    But did not get the correct answer which is w2 = < -7/3, -8/3, 1/3 >

    Where did I go wrong?
     
  2. jcsd
  3. Sep 8, 2012 #2
    Is that projection given? Because that doesn't jive with what I get.

    If you find the part of v that is parallel to the direction of w, then the only other part of v that remains must be perpendicular to w, no?
     
  4. Sep 8, 2012 #3
    That is the answer to the projection yes, I don't understand what you are trying to explain though?
     
  5. Sep 8, 2012 #4
    Okay, right, that projection is good. That is indeed the projection of [itex]v[/itex] onto [itex]w[/itex]. You could call it [itex]v_\parallel[/itex].

    The point I'm making is that, if [itex]a + b = c[/itex], then [itex]b = c - a[/itex], so if [itex]v_\parallel + v_\perp = v[/itex], then [itex]v_\perp = ?[/itex]
     
  6. Sep 9, 2012 #5
    Perfect I got the correct answer. So what your saying is by getting the projection of v onto w. It gives me a vector V which is parallel to W, and to get the component of that vector we subtract the original vector v by the parallel component " if we want the perpendicular component".

    Where I am confused is that there is a formula in my book for getting the component, and its in the form Comp v onto w = v*w/norm of v

    Why would using that be incorrect?

    Thank you for your help btw
     
  7. Sep 9, 2012 #6
    The component of v parallel to w is obtained by first calculating the unit vector in the direction of w (dividing w by its own magnitude), and then dotting v with that unit vector. The component perpendicular to w is obtained by subtracting the component parallel to w (times the unit vector in the direction of w) from v.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Vector component perpendicular
  1. Perpendicular vector (Replies: 1)

  2. Vector Perpendicular (Replies: 2)

  3. Perpendicular Vectors (Replies: 5)

  4. Component of a vector (Replies: 1)

Loading...