Just let it flow

Calculus Level pending

Find the flux of the vector field F ( r ) = 1 π r r 3 \vec{F}(\vec{r})=\frac{1}{\pi}\frac{\vec{r}}{||\vec{r}||^3} through the triangular surface S S with its vertices at ( 1 , ϕ , 0 ) , ( 0 , 1 , ϕ ) (1,\phi,0),(0,1,\phi) and ( ϕ , 0 , 1 ) (\phi,0,1) , where ϕ = 1 + 5 2 \phi=\frac{1+\sqrt{5}}{2} is the golden ratio.


The answer is 0.2.

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1 solution

Steven Chase
Dec 16, 2018

The triangular surface is one face of a convex regular icosahedron surrounding the origin. The total outward flux of 4 4 , divided by 20 20 faces gives a flux of 0.2 0.2 for each face.

Yes, exactly! I just stole your analogous problem about the cube and dressed it up a bit ;)

Otto Bretscher - 2 years, 5 months ago

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Yeah, that's a nice expansion which increases the challenge level a bit

Steven Chase - 2 years, 5 months ago

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