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Use Stokes' Theorem to find the circulation of F =4yi +3zj +7xk around the triangle obtained by tracing out the path (6,0,0) to (6,0,5), to (6,5,5) back to (6,0,0).
Circulation = ∫CF ⋅dr
 one year ago
 one year ago
Use Stokes' Theorem to find the circulation of F =4yi +3zj +7xk around the triangle obtained by tracing out the path (6,0,0) to (6,0,5), to (6,5,5) back to (6,0,0). Circulation = ∫CF ⋅dr
 one year ago
 one year ago

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wioBest ResponseYou've already chosen the best response.1
If you want to go from line integral to surface integral, shouldn't you need the anticurl?
 one year ago

wioBest ResponseYou've already chosen the best response.1
Nevermind, they gave the anticurl
 one year ago

wioBest ResponseYou've already chosen the best response.1
I mean A such that \[ B = \nabla \times A \]
 one year ago

wioBest ResponseYou've already chosen the best response.1
But apparently they gave it to you already.
 one year ago

?12Best ResponseYou've already chosen the best response.0
do you know how I would set up the line integral. I know that I have to use the points to make an equation of the triangle but after that I'm not sure
 one year ago

wioBest ResponseYou've already chosen the best response.1
So to use stokes theorem, you need to parametrize the surface.
 one year ago

wioBest ResponseYou've already chosen the best response.1
They don't want you to set up the line integral, but I can help you do that if you want.
 one year ago

?12Best ResponseYou've already chosen the best response.0
The surface is the triangle?
 one year ago

?12Best ResponseYou've already chosen the best response.0
I want to be able to do it using stoke's theorem/how they want it
 one year ago

wioBest ResponseYou've already chosen the best response.1
Here is stokes theorem: \[ \iint_S\mathbf{F}\cdot d\mathbf{S}=\int_{\partial S}\nabla \times \mathbf{F}\cdot d\mathbf{r} \]
 one year ago

wioBest ResponseYou've already chosen the best response.1
Now, the only way to use stokes theorem here is to do the left (surface integral) side. If you did the right (line integral side) would you really be using stokes?
 one year ago

?12Best ResponseYou've already chosen the best response.0
No. I guess I was making a mistake. So how would I parametrize the surface? After that would the surface integral require a normal?
 one year ago

?12Best ResponseYou've already chosen the best response.0
I'm getting line integrals and surface and green's theorem andstoke's theorem confused since we are barely covering them.
 one year ago

wioBest ResponseYou've already chosen the best response.1
You can easily find two parallel vectors for the triangle right?
 one year ago

wioBest ResponseYou've already chosen the best response.1
No, you do it by finding a vector between two points.
 one year ago

?12Best ResponseYou've already chosen the best response.0
Between two points. So would I have to use points not contained in the triangle?
 one year ago

wioBest ResponseYou've already chosen the best response.1
yeah so we want the bounds on the yz plane.
 one year ago

?12Best ResponseYou've already chosen the best response.0
okay so since I know the yz plane is parallel to the trianle would I be able to choose any 2 points there?
 one year ago

?12Best ResponseYou've already chosen the best response.0
oh so it is a projection onto the yz plane
 one year ago

?12Best ResponseYou've already chosen the best response.0
okay so does that tell me what the limits of integration for z are going to be or am I supposed to use it to parametrize the triangle?
 one year ago

wioBest ResponseYou've already chosen the best response.1
You could parametrize it as \[ \Phi(u,v) = (6,u,v),\quad 0\le u \le 5,\quad u\le v \le 5 \]
 one year ago

?12Best ResponseYou've already chosen the best response.0
Oh I see. Because the x value is constant, right? Then from there will I have to calculte the normal to dot it with the curl of F?
 one year ago

wioBest ResponseYou've already chosen the best response.1
In this case \(\mathbf{F}\) doesn't need to be messed with, you only take the curl to do the line integral part.
 one year ago

?12Best ResponseYou've already chosen the best response.0
So I just dot the parametrization of the triangle with the curl and then I just use the limits of integration for u and v?
 one year ago

wioBest ResponseYou've already chosen the best response.1
How many times do I have to say you don't take the curl?
 one year ago

?12Best ResponseYou've already chosen the best response.0
Sorry I keep looking up at the equation. Okay. What would be the next step in my process?
 one year ago

wioBest ResponseYou've already chosen the best response.1
\[ \iint_S \mathbf{F}\cdot d\mathbf{S}= \iint_D\mathbf{F}\circ\Phi(u,v)\cdot \frac{\partial \Phi}{\partial u}\times \frac{\partial \Phi}{\partial v}dudv \]
 one year ago

wioBest ResponseYou've already chosen the best response.1
\[ \mathbf{F}\circ \Phi(u,v) = \mathbf{F}(x(u,v),y(u,v), z(u,v)) \]
 one year ago

wioBest ResponseYou've already chosen the best response.1
\(D\) corresponds to the bounds of \(u,v\).
 one year ago

?12Best ResponseYou've already chosen the best response.0
okay so it is the vector field f in terms of u and v dotted with the normal of the parametrization?
 one year ago

?12Best ResponseYou've already chosen the best response.0
Okay I'm going to work it out really quick.
 one year ago

?12Best ResponseYou've already chosen the best response.0
Okay so when I did the normal I got <1,0,0> which, then dotted with <4u,3v,42> So I got 4u then I took the double integral \[\int\limits_{0}^{5}\int\limits_{u}^{5}4udv du\] that became \[\int\limits_{0}^{5}20u4u^2du\] from there I got \[10u^24/3u^3\] and my answer was 250/3. Did I mess up somewhere because my answer seems incorrect? Was my set up correct?
 one year ago

wioBest ResponseYou've already chosen the best response.1
You have to consider the orientation.
 one year ago

?12Best ResponseYou've already chosen the best response.0
the orientation is counter is wingspanwise so that means the normal is supposed to be supposed to be negative, right, or the parametrization of the triangle?
 one year ago

wioBest ResponseYou've already chosen the best response.1
Yes it should be negative.
 one year ago

?12Best ResponseYou've already chosen the best response.0
Okay I change the normal to negative and then my answer just ended up being 250/3 but it is still wrong. Does it look like I did a mistake in setting it up?
 one year ago

wioBest ResponseYou've already chosen the best response.1
Do you know what the answer is?
 one year ago

?12Best ResponseYou've already chosen the best response.0
Okay I got it I decided to use the parametrization that you gave me. Then I took the gradient of it and dotted it with the curl I got. so it was <3,7,4> dotted with the gradient of <6,u,v> which gave me 74 which is 3. Then I used all the limits of integration you gave me and got the correct answer which is 75/2 . I'm not sure if this is another part of the formula but it worked. Thank you very much! Would you gladly help me with one more wuestion if I post it up?
 one year ago
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