Wikipedia:Reference desk/Archives/Science/2021 June 18

= June 18 =

What glucose do to skeletal system?
Sentence: Blood flow and stream of glucose to the skeletal muscles increase.

What glucose do to skeletal system?

Source Rizosome (talk) 00:17, 18 June 2021 (UTC)


 * The skeletal muscles are the main muscles of the body, which we use in order to move (to fight or to run away, for example). Glucose, or blood sugar, is what fuels those muscles. The skeletal system is the bones that support our bodies, to which those muscles are attached. When we feel fear, blood flow increases and more glucose is supplied to the muscles, not the bones. nagualdesign 00:44, 18 June 2021 (UTC)
 * Note as well that the cells within the bones also need to be supplied with glucose to keep them alive. --Khajidha (talk) 23:02, 18 June 2021 (UTC)
 * Note also that skeletal muscles store glycogen, so are actually a source of glucose, not to mention that the increased blood flow is primarily to deliver oxygen, but this is a guy that hasn't quite mastered the rudiments of the English language and was simply tripping up over the word skeletal. nagualdesign 03:56, 19 June 2021 (UTC)

Galvanic cell question
In the article Galvanic cell, in the diagram at the top of the article, what happens if the porous disk (marked on diagram) is removed? Does the reaction proceed, but without generating an electric current? IBE (talk) 06:53, 18 June 2021 (UTC)
 * From Salt bridge:
 * "If no salt bridge were present, the solution in one half cell would accumulate negative charge and the solution in the other half cell would accumulate positive charge as the reaction proceeded, quickly preventing further reaction, and hence production of electricity."


 * nagualdesign</b></b> 17:05, 18 June 2021 (UTC)
 * ...Oh wait, I guess that's if there was still a non-porous barrier present. If there was no barrier the two solutions would mix and quickly react, and there would be no electricity production. <b style="font:1.3em/1em Trebuchet MS;letter-spacing:-0.07em"><b style="color:#000">nagual</b><b style="color:#BBA">design</b></b> 17:08, 18 June 2021 (UTC)

.....Could you explain why no current would flow if the porous barrier were removed and the electrolytes mixed? I know that various liquids other than deionized water work as the electrolyte for a cell with zinc and copper electrodes, such as damp earth, salt water, dilute acid, various vegetables and tap water. They may not be very useful for powering things, but I am surprised there would be zero open circuit voltage and zero current through a closed circuit. Edison (talk) 22:00, 18 June 2021 (UTC)

......The copper sulfate and zinc sulfate electrolytes are both prepared by exposing the two metals to sulfuric acid, so early 1800s experimenters  who created a voltaic cell by lowering zinc and copper electrodes into dilute sulfuric acid would have effectively created this cell, with the electrolytes mixed, as it sat there with no external current. Is there something special about the concentration of the electrolytes in the salt bridge cell? Edison (talk) 22:11, 18 June 2021 (UTC)
 * (note: changed formatting of Edison's post for readability): I think I get what you mean - the current (and voltage) might be affected, but it shouldn't be zero. I suppose the natural assumption is that the electrical charge has two ways of equalising: directly through solution, and "indirectly" meaning transport of electrons through the wire connecting the copper and zinc. Then the measured voltage would be reduced. Is that right? IBE (talk) 14:31, 19 June 2021 (UTC)

Principal axes of a tennis racquet
I drew File:tennis_racquet_principal_axes.svg based on the image on the right to illustrate the tennis racket theorem. The article's lede reads ... it is easy to throw the racket so that it will rotate around the handle axis (the third principal axis) without accompanying half-rotation around another axis; it is also possible to make it rotate around the vertical axis perpendicular to the handle (the first principal axis) without any accompanying half-rotation. ... Am I right that the third principal axis refers to &#234;1 whereas the first refers to &#234;3 in the diagram i.e. the numbering is swapped? If so, is the text wrong or the diagram wrong?

Thanks, cm&#610;&#671;ee&#9094;&#964;a&#671;&#954; 23:27, 18 June 2021 (UTC)
 * There seem to be three axes of rotation and three axes of translation. I’m not aware of a convention for numbering then. Edison (talk) 02:32, 19 June 2021 (UTC)
 * The diagram appears to be correct and the article states that the axis numbering is chosen so the moments of inertia are in order (so the numbering is uniquely defined given the three moments are different). The definitive (understandable) treatment of this is The Bizarre Behavior of Rotating Bodies by Veritasium at Youtube. Veritasium states (correctly) that the numbers are in ascending order while the article claims they are descending. Johnuniq (talk) 03:45, 19 June 2021 (UTC)
 * Thank you very much, and . I doubt Veritasium is a reputable source and don't have access to http://link.springer.com/article/10.1007%2FBF01049489 but another paper uses the convention I1≤I2≤I3 whereas the article uses I1&gt;I2&gt;I3. I've fixed the lede by referring to the notation used in the image and am leaving the prose for someone else to amend if needed. Cheers, cm&#610;&#671;ee&#9094;&#964;a&#671;&#954; 23:40, 19 June 2021 (UTC)
 * Veritasium is a reputable source, but perhaps not reliable in the Wikipedia sense. The article with, "The twisting tennis racket", uses the assumption that $$0<I_1<I_2<I_3.$$ I did not spot an explicit statement that the numbering of the moments of inertia corresponds to the numbering of the principal axes, but anything else would be madness without method in 't.  --Lambiam 08:18, 20 June 2021 (UTC)