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: [Dot Product] Vector Proection

  1. Nov 3, 2011 #1
    [Dot Product] Vector Projection

    1. The problem statement, all variables and given/known data


    2. Relevant equations



    3. The attempt at a solution

    I am not sure what to do here -- I know that the projection of u onto a "dotted" with w = 0 by definition, but I don't know how to show this.



    added this second part after plugging in for the definition of the projection we derived in class, then simplified. . .
    Last edited: Nov 3, 2011
  2. jcsd
  3. Nov 3, 2011 #2
  4. Nov 3, 2011 #3

    I like Serena

    User Avatar
    Homework Helper

    Hi Highway! :smile:

    You have an expression for the projection.
    Can you substitute that (and only that) in the formula you have for w?

    To show that 2 vectors are orthogonal, you need to show that their dot product is zero. That is, that [itex]\vec a \cdot \vec w = 0[/itex].

    What you need to know, is that there are calculation rules for dot products.
    For instance [itex]\vec a \cdot (\vec b+\vec c) = \vec a \cdot \vec b + \vec a \cdot \vec c[/itex].

    Can you simplify the expression for [itex]\vec a \cdot \vec w = 0[/itex]?
  5. Nov 3, 2011 #4
    Thanks!! I got it figured out :P

  6. Nov 3, 2011 #5

    I like Serena

    User Avatar
    Homework Helper

    Congrats! :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook