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!

Dot Product

  1. Mar 5, 2008 #1
    Three vectors x, y and z satisfy x + y + z = 0. Calculate the value of
    (x dot y) + (x dot z) + (y dot z) if the magnitude of x is 2, the magnitude of y is 3, and the magnitude of z is 4.

    Sorry I don't have time to format this properly, I've got to run off to work. This question has been bugging me, and any help would be greatly appreciated.
     
  2. jcsd
  3. Mar 5, 2008 #2

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Dot your equation with x, y and z, and add the results and see something fun happening.
     
  4. Mar 5, 2008 #3
    Sorry, but I'm not sure I follow.
     
  5. Mar 5, 2008 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Do a bit at a time!

    Hi Fineline! Welcome to PF! :smile:

    (btw, it's ok to write x.y + x.z + y.z, once you've made it clear that x y and z are vectors.)

    Yes, I don't follow either: x.y etc is a scalar, so you can't dot it with anything. :frown:

    Hint: Can you calculate x.y + x.z? And then … :smile:
     
  6. Mar 5, 2008 #5
    I do not have any experience with these problems, so I don't know the standard way to approach it. One possible approach, however, is to find what (x + y + z)2 is when expanded.
     
  7. Mar 5, 2008 #6

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    ooo! Your method is even nicer than mine! :blushing:
     
  8. Mar 5, 2008 #7

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You have an arithmetic operation. (dot product) Use it. In as many ways as you can imagine.
     
  9. Mar 5, 2008 #8
    Alright, thanks everyone, I got it all worked out.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Dot Product
  1. Dot product (Replies: 2)

  2. Dot product (Replies: 1)

  3. Dot product (Replies: 5)

  4. Dot product (Replies: 1)

Loading...