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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> extropy-chat <extropy-chat-bounces@lists.extropy.org> <b>On Behalf Of </b>Ben Zaiboc via extropy-chat<br><br><o:p></o:p></p></div></div><p class=MsoNormal><br>>…That would mean short, fat cylinders, not long thin ones, no?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Hi Ben,<o:p></o:p></span></pre><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Ja, or we attach masses on the rim in order to make the axis of rotation the maximum moment of inertia.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><br>>…It's interesting that we hadn't really understood this until relatively recently. Makes me wonder what other physics we are still completely in the dark about.<br><br><o:p></o:p></p><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>We were weren’t really in the dark on this one. Granted the weightless environment offered a lot of cool chances to do stuff like this (and by the way… do you ever wonder what we are STILL doing in the space station?)<o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>I could write on and on about this topic, but perhaps at some point you saw a toy which looks like ¾ of a sphere with a cylinder attached. The physics teacher spins the tippy top, it turns upside down:<o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><a href="https://www.real-world-physics-problems.com/tippe-top.html#:~:text=The%20tippe%20top%20is%20a,in%20an%20upside%2Ddown%20orientation">https://www.real-world-physics-problems.com/tippe-top.html#:~:text=The%20tippe%20top%20is%20a,in%20an%20upside%2Ddown%20orientation</a>.<o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>She asks her students: did the CG of the tippy top rise in inversion? Clearly it did. And so… how and why? Did it borrow energy from the universe somehow? And if so, is the universe willing to loan some more of that? etc.<o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>We love this one, because it is a rare example of where guys with the physics degrees don’t always understand it but the controls engineers do. <o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Usually the physics jockey hafta explain everything to us bonehead engineers, but we show them this, which appears to defy conservation of energy. It doesn’t, and it isn’t magic. We controls engineers have equations which deal with products of inertia and even have that icky coefficient of friction that physicists don’t like to deal with, all those distasteful non-linearities, swoon.<o:p></o:p></span></pre><p class=MsoNormal><br>>…I'm also wondering if a long thin cylinder flipping about a perpendicular axis would be the disaster…<br><br><o:p></o:p></p><pre>-- <o:p></o:p></pre><pre>Ben Zaiboc<o:p></o:p></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>That isn’t what happens. More later if I get time.<o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>spike<o:p></o:p></span></pre><pre><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></pre></div></body></html>