Checking $\nabla x (uv(hat))$ Equation

  • Thread starter Thread starter squenshl
  • Start date Start date
Click For Summary

Homework Help Overview

The discussion revolves around verifying the vector calculus identity involving the curl of a product of a scalar function and a vector field, specifically checking the expression \nabla x (uv(hat)) = (\nablau) x v(hat) + u(\nabla x v(hat)). The subject area is vector calculus.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants suggest expressing the identity in terms of components and calculating derivatives to verify the identity. There are questions about the necessity of using Cartesian coordinates and definitions related to determinants, gradients, and cross products.

Discussion Status

Some participants have provided guidance on how to approach the problem by working through components and comparing both sides of the equation. There is an acknowledgment that this is a common type of problem encountered in studies, and the original poster has indicated that this is related to test preparation.

Contextual Notes

There is a note from a moderator emphasizing the need for the original poster to show an attempt at solving the problem, in line with the forum's homework guidelines.

squenshl
Messages
468
Reaction score
4
How do I check [tex]\nabla[/tex] x (uv(hat)) = ([tex]\nabla[/tex]u) x v(hat) + u([tex]\nabla[/tex] x v(hat)).
 
Physics news on Phys.org
squenshl said:
How do I check [tex]\nabla[/tex] x (uv(hat)) = ([tex]\nabla[/tex]u) x v(hat) + u([tex]\nabla[/tex] x v(hat)).

Changing your notation a little, if f(x,y,z) is a scalar and

V(x,y,z) = <u(x,y,z),v(x,y,z),w(x,y,z)> is a vector, to show

[tex]\nabla \times f\vec V = \nabla f \times\vec V + f\nabla \times \vec V[/tex]

just work both sides out in terms of components and compare. I don't think it matters whether V is a unit vector.
 
The same way you prove every other vector calculus identity... express everything in terms of components, calculate the derivatives and simplify.

Even if this isn't an assigned homework problem, it's still a homework type problem and you should follow the homework template.
 
What if I wanted to use Cartesian coordinates, the definitions of the determinant, gradient and cross product of 2 vectors.
 
squenshl said:
What if I wanted to use Cartesian coordinates, the definitions of the determinant, gradient and cross product of 2 vectors.
As a matter of fact, you pretty much have to use all of those. And work things out in terms of components of vectors, as others have said.

Is this homework?
 
Na. Studying for a test. It was a on a practice test.
 
squenshl said:
Na. Studying for a test. It was a on a practice test.

Moderator's note:

I have moved this thread to the Homework & Coursework Questions area. We have guidelines on what belongs there, and this definitely qualifies.

At this point, normal rules for Homework & Coursework apply. The OP should show an attempt at solving the problem before further help is given.
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
6
Views
2K
Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
20
Views
2K