MHB Compute the downwards flux of F

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The discussion focuses on calculating the downward flux of the vector field F over a specified surface S. The vector field is defined as F(x,y,z) = i cos(y/z) - j (x/z) sin(y/z) + k (xy/z^2) sin(y/z). The downward flux is expressed as a double integral involving the component of F in the k-direction, specifically simplifying to the integral of xy sin(y) over the surface where z=1. The user is encouraged to proceed with the calculations based on the provided setup. The conversation emphasizes the importance of correctly interpreting the vector field and surface for accurate flux computation.
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Uniman said:
https://www.physicsforums.com/attachments/418
The work done so far

https://www.dropbox.com/s/qmfidqot3nttlw5/phpQd8GGH.png
https://www.dropbox.com/s/xn4t5m2aleopwy7/phpldZ0KX.png

Is the answer correct...

Hi Univman, :)

The links to your work on the problem seem not to work. Anyway, you have been given the vector field,

\[\mathbf{F}(x,y,z)=\mathbf{i} \cos\left( \frac{y}{z}\right)-\mathbf{j} \frac{x}{z} \sin \left(\frac{y}{z}\right)+\mathbf{k} \frac{xy}{z^2} \sin \left( \frac{y}{z} \right)\]

The downward flux of \(\mathbf{F}\) over \(S\) is given by,

\[\iint_{S}\mathbf{F}.(-\mathbf{k})\,dS=-\iint_{S}\mathbf{F}.\mathbf{k}\,dS=-\iint_{S}\frac{xy}{z^2}\sin\left(\frac{y}{z}\right)\,dS\]

On the surface \(S\); \(z=1\). Therefore we have,

\[\iint_{S}\mathbf{F}.(-\mathbf{k})\,dS=-\iint_{S}xy\sin y\,dS=-\int_{x=0}^{1}\int_{y=0}^{\pi}xy\sin y\,dy\,dx\]

Hope you can continue. :)

Kind Regards,
Sudharaka.
 
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