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Post by striker16 on Sept 27, 2012 14:45:19 GMT 1
When Laithwaite is holding the spinning wheel, after he has made it precess, it seems light as a feather and he has to apply very little effort to manipulate it. This is because when a spinning wheel is precessing like this its center of mass shifts centrally, so at the point at which Laithwaite is holding the shaft, which is attached to the wheel at the other end, very little mass is felt. The only reason people think the wheel is 'rising' is because its precession has be made to follow this trajectory due to an applied torque, which is what Laithwaite does, so there is really no magic happening here. The fact is that none of the mass of a spinning wheel can suddenly disappear because it will contain the same amount of material as when not spinning. It is the transfer of mass due to its circular motion that is displaced from where it would normally be when not spinning. A discus travelling through the air does not lose mass but its mass is displaced by a linear motion provided by the discus thrower, which is why is simply does not fall to the ground when released. Again, this is all covered by Newton's basic laws.
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Post by mrsonde on Sept 27, 2012 20:00:19 GMT 1
mrsonde, among all your vitriol Sigh. How many times have I been through this one on messageboards - this one in particular, actually. I urge you most sincerely to look through this thread very carefully, with as objective a view as you might be able to summon. I suggest if you're so sensitive that you register a rejection of your basic errors in the understanding of physics as "vitriol", you really shouldn't start insulting people who have a better grasp of the subject than you do, and have offered to help you understand the matter under discussion. To lift. It was hitherto unrecognised, yes, that much is true. But as I've explained, it is a consequence of Newtonian mechanics. I've explained that, you twit! Don't you read these posts? Laithwaite never said anything different. He merely pointed out that this consequence of the laws of motion had been completely overlooked. There is no "obsession". It is however a fascinating phenomenon, and one that no physicist had noticed before Laithwaite, and as far as I've been able to find has been able to explain. Therefore it's an interesting subject to discuss on a science board - from a purely scientific point of view, or indeed as a fascinating datum in the history or indeed philosophy of science. At the very least, it's revealed to yourself that you didn't know the first thing about the physics of motion, didn't it?
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Post by mrsonde on Sept 27, 2012 20:07:55 GMT 1
No, most of that is wrong. I'll return to my mulling. You might find this video of intrest if the link works, the bit towards the end where he is stood on the lazy susan is facinating.No gearing conections and yet the turntable rotates. www.youtube.com/watch?v=0k276y9kuQQ&feature=relatedYes, that last bit is indeed directly relevant. In the Laithwaite demo, he's performing the same experiment, except in reverse - he's spinning, therefore the angle of the shaft is lifting into the vertical.
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Post by mrsonde on Sept 27, 2012 20:09:32 GMT 1
If you have a mull about it there does not seem any reason why there could not be an upwards loss of weight.. No, indeed.
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Post by mrsonde on Sept 27, 2012 20:19:29 GMT 1
When Laithwaite is holding the spinning wheel, after he has made it precess, it seems light as a feather and he has to apply very little effort to manipulate it. This is because when a spinning wheel is precessing like this its center of mass shifts centrally No, it doesn't. The centre of mass stays where it is, in the centre of the wheel. The wheel precesses due to the torque, that's all. If he resists the torque, he will need to expend force to do so - no shift in the centre of mass occurs. Well, this is a new one. The previous suggestion was that the CoM had moved closer to Laithwaite, not farther away! Where is it going now then? No, there's no magic. Why does the wheel rise because of its precession, do you reckon? The precession, for your information - for the fifth time counting I think - is parallel to the ground. Yes - I've told you that three times already. Fine - you've finally got that point. Shut up about mass now, would you? Ffs! This is a Hogwarts seminar again. Kindly find any link that mentions any principle of physics anywhere anywhen by anywhom that mentions such a "transfer of mass"!! No. You need a basic primer lesson in CSE Physics. "Inertia" does not mean "displacement of mass". Nothing does, in fact. Bollocks. Where in any of Newton's three laws is there any mention of "mass" being displaced?
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