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: Sketching vector fields

  1. Mar 31, 2009 #1
    1. The problem statement, all variables and given/known data

    I am asked to sketch the following vector field in the xy-plane

    (a) F(r) = 2r

    (b) F(r) = -r/||r||3

    (c) F(x,y) = 4xi + xj

    2. Relevant equations

    3. The attempt at a solution

    Can someone please give me some hints on how to proceed
  2. jcsd
  3. Mar 31, 2009 #2


    User Avatar
    Homework Helper

    hi EquinoX

    first I would look at the direction and magitudes of the vectors & see if you can spot any symmetries

    a good way to start is to sketch the vector at several points as well
  4. Mar 31, 2009 #3
    yes but for F(r) = 2r this is a 3D vector field, so if I am asked to sketch it in an xy plane, do I just look at the i + j direction? and is 2r basically just 2xi + 2yj + 2zk?

    because r is xi + yj + zk?
    Last edited: Mar 31, 2009
  5. Mar 31, 2009 #4


    User Avatar
    Homework Helper

    Yeah i think that should do

    r = sqrt(x^2 + y^2 + z^2) and in the xy plane z = 0, so this shouldn't affect your r anyway
  6. Mar 31, 2009 #5
    so r = sqrt(x^2)i + sqrt(y^2)j ?
  7. Mar 31, 2009 #6


    User Avatar
    Homework Helper

    sorry bit of confusion over notation
    |r| = sqrt(x^2 + y^2 + z^2)

    r = xi + yj + zk
  8. Mar 31, 2009 #7
    I am asking 2r?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook