Timeline for Lagrange Multipliers and Virtual Work: Are Joos & Freeman wrong?
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| May 13, 2016 at 17:20 | comment | added | Steven Thomas Hatton | The presentation may have lost something in translation. The salient point I take from it is that the $\delta x_i$ can all be treated as arbitrary if the values of the $\lambda_k$ are appropriately chosen. To me, this seems important because the principle of virtual work does not necessitate displacement consistent with the given system of constraint. There are times when varying a constraint produces that desired result. A simple example is the imagined variation in the length of a member in a truss, and determining the change in potential energy that would result. | |
| May 13, 2016 at 3:59 | comment | added | Qmechanic♦ | Obviously the argument can be fitted to any subset of $\ell$ columns of the rectangular matrix, e.g. the $\ell$ last columns, or the $\ell$ first columns, but yeah, that's confusing writing. | |
| May 13, 2016 at 0:04 | comment | added | Steven Thomas Hatton | I stand corrected. It's in the same section at the bottom of page 116. "Exactly as in the statical case, we can dispose of the $l$ quantities $\lambda_k$ so that the first $l$ parentheses vanish." | |
| May 12, 2016 at 5:07 | history | edited | Qmechanic♦ | CC BY-SA 3.0 |
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| May 11, 2016 at 21:11 | comment | added | Qmechanic♦ | @StevenHatton : Which next Section? Which page? | |
| May 11, 2016 at 20:00 | comment | added | Steven Thomas Hatton | While I agree that relabeling the coordinates as you suggest will work, I note that Joos turns around in the next section and attacks the first $l$ terms, rather than the last ones. As if to say, "if you think I made a mistake, think again". | |
| May 11, 2016 at 18:59 | history | answered | Qmechanic♦ | CC BY-SA 3.0 |