This stuff is quite misleading. One has to put energy in first to get the moving magnet into its starting position. So there is no energy gain.
On Tue, Sep 4, 2012 at 6:09 AM, Giovanni Santostasi <gsantost...@gmail.com>wrote: > How is this an epicycle? > > A biological system is complicated and even if it has to obey the law of > physics, it is not usually a good starting example to introduce basic > physics concepts. > > In some cases (teaching physics to biomed students) could be a good idea > to mention examples like this in introductory physics class to show how the > real physical world is more complicated than the toy models we use. > > The physics of a muscle is relatively well known though, and the > explanation I have given is both valid theoretically but also validated > experimentally at least as first approximation. > > But if one looks at things in fine details in biological systems, things > can go complicated pretty quickly: > http://www.ncbi.nlm.nih.gov/pubmed/11383139 > > For your information and to give you some of my background, I have a PhD > in astrophysics (I now work in Neuroscience) and I have taught physics at > the college level for 8 years. > > Giovanni > > > On Mon, Sep 3, 2012 at 10:54 PM, Jouni Valkonen > <jounivalko...@gmail.com>wrote: > >> >> On Sep 4, 2012, at 6:30 AM, Giovanni Santostasi <gsantost...@gmail.com> >> wrote: >> >> >> What happens is that your muscles are like springs and they are >> getting stretched by the weight. When they are stretched beyond a point the >> muscle pulls back and then relaxes, this over and over again and this >> oscillatory motion does indeed work. >> >> >> Somehow this explanation reminds me that annoying anomaly in classical >> physics is just explained away by inventing epicycles. Classical physics is >> based on simplified conception of reality. It does not deal with gravity >> and permanent electromagnetic forces that are making bodies rigid and >> solid. >> >> I still think that Terry's explanation is incomplete, because I assume >> that permanent magnets are demagnetised more slowly if magnets are cooled >> significantly. If neodymium magnets are heated close to 80ºC, the will >> demagnetise very rapidly. And my assumption is that demagnetisation rate is >> close to zero near absolute zero. >> >> —Jouni >> > >
