# Homework Help: Need to find the source for a 3D Hooke's law equation to cite

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1. Jul 22, 2015

### datahead8888

1. The problem statement, all variables and given/known data
I am using the 3D implementation of Hooke's law as found in wikipedia at: https://en.wikipedia.org/wiki/Hooke's_law
I need to find the actual source to cite it in a master's project software write up. Many professors do not consider wikipedia to be an acceptable source, from what I've heard.

2. Relevant equations

\begin{bmatrix}
\sigma_{11} \\
\sigma_{22} \\
\sigma_{33} \\
\sigma_{23} \\
\sigma_{13} \\
\sigma_{12}
\end{bmatrix}
=
\begin{bmatrix}
2 \mu + \lambda & \lambda & \lambda & 0 & 0 & 0 \\
\lambda & 2 \mu + \lambda & \lambda & 0 & 0 & 0 \\
\lambda & \lambda & 2 \mu + \lambda & 0 & 0 & 0 \\
0 & 0 & 0 & \mu & 0 & 0 \\
0 & 0 & 0 & 0 & \mu & 0 \\
0 & 0 & 0 & 0 & 0 & \mu
\end{bmatrix}
\begin{bmatrix}
\varepsilon_{11} \\
\varepsilon_{22} \\
\varepsilon_{33} \\
2 \varepsilon_{23} \\
2 \varepsilon_{13} \\
2 \varepsilon_{12}
2\end{bmatrix}

3. The attempt at a solution
I skimmed through the cited Walter Lewin MIT course lectures and did not see it.
I found the cited book "Advanced Strength and Applied Elasticity" on Google books, but it omits major pages.
I just need to know for certain where it comes from to cite it properly. I would like to avoid tracking down a copy of a hard book if possible, especially if I don't know the book has what I need.

2. Jul 22, 2015

### cpsinkule

Your options are:
Find the book somehow and make sure it's in there and the page
Cite Wikipedia
Derive it from your own principles
The honest thing to do is to cite the Wiki page because that's where you honestly got the information.

3. Jul 22, 2015

### datahead8888

> The honest thing to do is to cite the Wiki page because that's where you honestly got the information.

When I went to the orientation for grad school, a professor told everyone not to cite wikipedia when writing academic papers in conferences. He said this is "laughed at". He said that if you see something you like, find the source that wikipedia cites, and cite that instead. This is a masters project write up and not an academic paper, but it is still evaluted by professors who write papers.

If the university library has the book, I could track it down, though there is no guarantee it has the formula. I just wanted to see if anyone online might know for certain of a source that has it. If it's an online, viewable source, that would instantly resolve it.

The other option would be to find another usable formula from an easy to find source and recode it in the C++ code then retest. I'd really like to try to find it first, though.

4. Jul 22, 2015

### cpsinkule

I would think you have some leeway with this formula. I would cite the only book wiki cites and if it's not there it would be wiki's fault for not citing their sources. Normally I don't condone plagiarism, but hookes law is certainly not original work at this point and I don't think whoever reviews your presentation is going to look through the book to verify it. No one cites newton's principia when they mention f=ma in a paper.

5. Jul 23, 2015

### rock.freak667

I agree with cpsinkule, if you state it as Hooke's Law, I don't think anyone will question you as to where you got it from. As if that is the case and you need to reference every single thing, then you might as well start looking for references for things like area = πr2 or even more absurd 1 + 1 = 2.

6. Jul 23, 2015

### SteamKing

Staff Emeritus
This is not something which was discovered in a field etched on gold sheets.

You should be able to find a reference for Hooke's Law for isotropic materials in any standard text on elasticity or advanced strength of materials. If you can't find the Ugural work online, there are many others.

These are basic relationships which should be familiar to anyone who has studied in this field. Unearthing a source for it is similar to finding one for F = ma.

7. Jul 24, 2015

### William White

I don't think it is necessary to cite long-established, widely known laws.

Writing, "via Hooke's Law, it can be shown..." etc. is fine.

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