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!

Am i doing this right?

  1. Jan 27, 2004 #1
    Here's the question:

    Suppose we have a scalar field phi(r)=xy defined on the plane (x,y). Find th vector field gradient phi, and plot the result in a single graph atthe four points (1,1), (-1,1) (1,-1), (-1,-1) and at the four points (1,0),(0,1),(-1,0) and (0,-1).

    Ans.

    For the gradient of phi(r)=xy, I got yi + xj. Is this right?
     
  2. jcsd
  3. Jan 27, 2004 #2
    one more questio

    how will I plot it. Do i have to solve the eequation at each of those points and plot the answer that I get?
     
  4. Jan 27, 2004 #3

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yes.
     
  5. Jan 27, 2004 #4

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: one more questio

    No, it's not that involved. For each of the 4 points, you plug in the values of x and y (edit: plug them into the gradient). From those, you will get 4 vectors, which you need to sketch on the graph.
     
  6. Jan 27, 2004 #5
    is this right ?

    Okay. So at (1,1) it would be i + j
    at(-1, 1)= -i
    at (1,-1) = i-j
    at (-1,-1) = -i-j

    How would I plot it?
     
  7. Jan 27, 2004 #6

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: is this right ?

    Right.

    These are wrong. Remember that for your vector v, grad(v)=yi+xj.

    This one is OK.

    Go to the point in question and let that be the origin of a vector whose components are what you calculated them to be. For instance, in the first case go to the point (1,1) and draw the vector i+j.

    Also, don't forget to do the same for the other 4 points listed. You will have 8 vectors in all.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Am i doing this right?
  1. Am I doing this right? (Replies: 4)

  2. Am I doing this right? (Replies: 3)

  3. Am I Doing this right? (Replies: 2)

  4. Am i doing this right (Replies: 1)

  5. Am I doing this right? (Replies: 1)

Loading...