/sci/ - Science & Math » Thread #14186848

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Anonymous Fri 04 Feb 19:21:39 2022 No.14186848 View Reply Original Report

Quoted By:

I hate physics textbooks

Anonymous

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Anonymous Fri 04 Feb 2022 19:25:36 No.14186866 Report

Quoted By: >>14186925 >>14186989

did you think "left for an exercise for the reader" was a joke?

Anonymous

Anonymous Fri 04 Feb 2022 19:35:57 No.14186910 Report

Quoted By: >>14186930

i have never seen a single correct derivation in a physics textbooks. all hand waving what's the point? just put the formula and begin exercises

Anonymous

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Anonymous Fri 04 Feb 2022 19:37:45 No.14186915 Report

Quoted By:

Anonymous

Anonymous Fri 04 Feb 2022 19:39:31 No.14186925 Report

Quoted By: >>14186931

>>14186866
This doesn't prove that it's a weak derivative.

Anonymous

Anonymous Fri 04 Feb 2022 19:41:28 No.14186930 Report

Quoted By:

>>14186910
its to give motivation for why something is plausible.

Anonymous

Anonymous Fri 04 Feb 2022 19:41:36 No.14186931 Report

Quoted By: >>14186952

>>14186925
that delta implies the entire expression belongs in an integrand, baby

Anonymous

Anonymous Fri 04 Feb 2022 19:42:03 No.14186933 Report

Quoted By:

Physicists are retarded. More news at 7

Anonymous

Anonymous Fri 04 Feb 2022 19:48:10 No.14186952 Report

Quoted By:

>>14186931
Ok, but now show that integrating a function against the divergence returns the function evaluated at the point the field is centered.

Anonymous

Anonymous Fri 04 Feb 2022 20:02:43 No.14186989 Report

Quoted By: >>14187004

>>14186866
Here's how an actual physicist would do it in standard notation
$\partial_i \left(r_k r_k\right)^{n/2} = \frac{n}{2}\left(r_k r_k\right)^{n/2-1}2r_i = n\left(r_k r_k\right)^{(n-1)/2}\hat{r}_i$

Not so hard is it?

Anonymous

Anonymous Fri 04 Feb 2022 20:07:55 No.14187004 Report

Quoted By: >>14187030

>>14186989
same thing, just more abbreviated. i'm writing some appendices for an interdisciplinary project where i assume the reader has virtually no knowledge of the subjects at hand, so i kept notation to a minimum.

Anonymous

Anonymous Fri 04 Feb 2022 20:18:26 No.14187030 Report

Quoted By: >>14187036

>>14187004
You will end up scaring them with your long derivation with "unabbreviated" notation. That's not a good trade off. Stick in summation symbols instead of using Einstein convention, but you are making the derivation needlessly long. imo.

Anonymous

Anonymous Fri 04 Feb 2022 20:22:03 No.14187036 Report

Quoted By:

>>14187030
>making the derivation needlessly long
agreed. it could be a lot shorter.
also agree about the einstein notation. i think it's just too powerful unless you are already familiar with the subject

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