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Natural Science Forum / Physics / General Physics / July 2008Gyroscope
In a famous experiment in the Christmas lectures in London Prof Eric Laithwaite had a small boy lift a huge gyroscope when not spinning. the boy could hardly lift it. He then set it spinning and the boy could lift it easily. Now when you push on a gyro it precesses and produces a torque at right angle to the force you apply. How was the boy able to lift the spinning mass but not the stationary one? K. >In a famous experiment in the Christmas lectures in London Prof Eric >Laithwaite had a small boy lift a huge gyroscope when not spinning. >the boy could hardly lift it. He then set it spinning and the boy >could lift it easily. Now when you push on a gyro it precesses and >produces a torque at right angle to the force you apply. How was the >boy able to lift the spinning mass but not the stationary one? Judging from the picture at #10 on http://www.gyroscopes.org/1974lecture.asp, I would say the reason is that he wasn't lifting it straight either time. But if it is spinning in the right direction, then the lifting shown at #10 really would be easier, since all Denis would have to do is push to the right -- not fighting gravity -- and the gyroscope would precess upward. But for a more detailed explanation of what is really going on in these lectures, see: http://www2.eng.cam.ac.uk/~hemh/gyroscopes/htmlgyroscopes.html for the correct explanation of what was really going on. | In a famous experiment in the Christmas lectures in London Prof Eric | Laithwaite had a small boy lift a huge gyroscope when not spinning. [quoted text clipped - 4 lines] | | K. Your memory is at fault, or your description is. The effort to lift a spinning gyroscope vertically is identical to the same gyro not spinning. I suspect the child was unable to rotate the axis of the spinning gyro, whereas the still gyro applied a torque to his wrist, the lift being single handed at one end of the axis. > <kronec...@yahoo.co.uk> wrote in message > [quoted text clipped - 13 lines] > spinning gyro, whereas the still gyro applied a torque to his wrist, > the lift being single handed at one end of the axis. Have a look at this... http://www.springerlink.com/content/p371t405258757r2/ K. | > <kronec...@yahoo.co.uk> wrote in message | > [quoted text clipped - 17 lines] | | http://www.springerlink.com/content/p371t405258757r2/ Nothing there but advertising for some book by A. L. Dmitriev and V. S. Snegov whom nobody has ever heard of. What's your point? You want me to waste my money on it? You think I was born yesterday? Ships can carry huge gyroscopes to stabilize them but they still displace the same amount of water, spinning it not. http://en.wikipedia.org/wiki/Anti_rolling_gyro "Effective ship installations require approximately 3% to 5% of a vessel's displacement." Maybe you are still wet behind the ears but there are no anti-gravity devices and Laithwaite was not attempting to say there are. He was demonstrating the attitude of the gyro, not any change in it's weight as you seem to be suggesting. > <kronec...@yahoo.co.uk> wrote in message > [quoted text clipped - 34 lines] > demonstrating the attitude of the gyro, not any change in it's weight > as you seem to be suggesting. You obviously have difficulty reading so I will help you. Maybe you are Autistic. This is not a book - it is a journal paper Abstract An experiment on the weighing of two coupled mechanical gyroscopes with zero total angular momentum is described. Possible reasons for the observed difference in the masses of the gyroscopes with vertical and horizontal orientations of their spin axis are discussed. Try reading it! K. | > <kronec...@yahoo.co.uk> wrote in message news:7c7c5348-b0ce-4e18-95e7-ed01481681ae@i20g2000prf.googlegroups.com... | > | On Jul 29, 12:23 pm, "Androcles" <Headmas...@Hogwarts.physics> wrote:| > <kronec...@yahoo.co.uk> wrote in message [quoted text clipped - 34 lines] | | You obviously have difficulty reading so I will help you. Don't bother, you are a obviously a troll and a cretin. f.ck off. *plonk* To ya All Spinning or not spinning the gyro weighs the same. The answer than is in leverage. Once set spinning its axis is horizontal and the wheel is vertical. The round bars of the gyro are easier for the boy to lift straight up. When not spinning the gyro is on its side I relate this to lifting a man who is standing (vertical),and to one lying on the ground (horizontal) I got a toy gyro for my 8th birthday and still have it. When spinning it still amazes me Seems to defy gravity. I love my little gyro Bert In sci.physics, HardySpicer <gyansorova@gmail.com> wrote on Mon, 28 Jul 2008 22:10:38 -0700 (PDT) <44afdca3-d4ef-4d91-be4f-11cd0db3f2e6@b1g2000hsg.googlegroups.com>: >> <kronec...@yahoo.co.uk> wrote in message >> [quoted text clipped - 4 lines] >> | > | In a famous experiment in the Christmas lectures in London Prof Eric >> | > | Laithwaite had a small boy lift a huge gyroscope when not spinning. Note: http://en.wikipedia.org/wiki/Eric_Laithwaite mentions that experiment, though a diagram would be nice. ;-) Some of his notions apparently border on the crankish -- e.g., that moths use short wave radio to communicate between males and females. (He persisted even after the actual communication mechanism -- a chemical pheromone -- was isolated and analyzed.) http://www.sptv.demon.co.uk/gyro.htm is one possible configuration for this "lifting" device. Personally, I think most of the effect is explainable by force or torque on the bearings, though I'd have to work it out. I do know that a spinning gyroscope can be supported by one of its pivot points, with the other precessing around it. The post, presumably, is seeing the weight of the entire gyroscope. I don't know the effect if a force is applied to the unsupported end while it's precessing. http://www2.eng.cam.ac.uk/~hemh/gyroscopes/htmlgyroscopes.html shows a toy device with a support, among other devices. It's not magic, of course. >> | > | the boy could hardly lift it. He then set it spinning and the boy >> | > | could lift it easily. Now when you push on a gyro it precesses and [quoted text clipped - 29 lines] > You obviously have difficulty reading so I will help you. Maybe you > are Autistic. Be advised that anyone who doesn't agree with Androcles is a troll and a cretin. ;-) > This is not a book - it is a journal paper > [quoted text clipped - 7 lines] > > K.  Signature#191, ewill3@earthlink.net Useless C++ Programming Idea #8830129: std::set<...> v; for(..:iterator i = v.begin(); i != v.end(); i++) if(*i == thing) {...} ** Posted from http://www.teranews.com ** | In sci.physics, HardySpicer | <gyansorova@gmail.com> | wrote | on Mon, 28 Jul 2008 22:10:38 -0700 (PDT) | <44afdca3-d4ef-4d91-be4f-11cd0db3f2e6@b1g2000hsg.googlegroups.com>: | >> <kronec...@yahoo.co.uk> wrote in message news:7c7c5348-b0ce-4e18-95e7-ed01481681ae@i20g2000prf.googlegroups.com... | > <kronec...@yahoo.co.uk> wrote in message | >> [quoted text clipped - 4 lines] | Note: http://en.wikipedia.org/wiki/Eric_Laithwaite mentions | that experiment, though a diagram would be nice. ;-) Wherein it says "Laithwaite used a large gyroscope located on the end of a long rod." How much intelligence does it take to figure out what the long rod is for? If you can bench press 200 lbs then you can lift 200 lbs, but not on the end of a long rod. Personally I have difficulty lifting a grocery bag. Note that the long rod was entirely omitted in Kronecker's description. Perhaps it was a magic wand, huh? | Some of his notions apparently border on the crankish | -- e.g., that moths use short wave radio to communicate [quoted text clipped - 20 lines] | | It's not magic, of course. That leads to http://www2.eng.cam.ac.uk/~hemh/boomerangs.htm where the movie by Hugh Hunt contains a bicycle wheel on the end of a "long rod", supported by a "long string". | >> | > | the boy could hardly lift it. He then set it spinning and the boy | >> | > | could lift it easily. Now when you push on a gyro it precesses and [quoted text clipped - 32 lines] | Be advised that anyone who doesn't agree with Androcles | is a troll and a cretin. ;-) Very observant of you, Ghost. I see you have the wisdom not to disagree with me, although it would be more correct to say that anyone who doesn't agree with Androcles is a troll OR a cretin. The "or" is an inclusive "or". In the case of "HardySpicer" the "and" does apply. Being a cretin he will not learn from your advice but change his name and try again to discredit me. > | Be advised that anyone who doesn't agree with Androcles > | is a troll and a cretin. ;-) [quoted text clipped - 5 lines] > "and" does apply. Being a cretin he will not learn from your advice > but change his name and try again to discredit me. Oh, but nobody can discredit you more than you do yourself. > How much intelligence does it take to figure out what the long rod is for? > If you can bench press 200 lbs then you can lift 200 lbs, but not on > the end of a long rod. Interesting how the memory plays tricks. I watched the program live and remember it being quite a heavy weight but now that I check I find it was only 18lbs + 6lbs for the shaft. Video here.. http://gyroscopes.org/1974lecture.asp | > How much intelligence does it take to figure out what the long rod is for? | > If you can bench press 200 lbs then you can lift 200 lbs, but not on [quoted text clipped - 4 lines] | only 18lbs + 6lbs for the shaft. Video here.. | http://gyroscopes.org/1974lecture.asp Well, 18 lbs is a large bowling ball, I wouldn't want to hold that at arm's length with my arm horizontal for very long, although lifting it vertically is within my capability... just. If you put what you see on TV in terms of what you actually experience for yourself you'll often find a lot of it is hype. Having said that I decided to watch that piece of video. Back in the days when I rewound electric motors for a living I used to degrease ball races, and holding them in the centre use an airline to flush out the solvent. It is quite easy to aim the air jet to get the outer race spinning and a worn bearing will reveal its condition by vibrating. Anyway, one day I dropped one. It hit the tarmac, sparks flew as it ground itself on the stone, then it took off into a flock of gulls, killing one and finally dropped into number two basin in Chatham Dockyard. If that kid had dropped the gyro it would have hit the floor, spinning, gripped and taken off, ripping into the audience and killing or causing serious injury. If I'd been present that demo would not have taken place in that form, it was a bloody dangerous thing to do. >Have a look at this... > >http://www.springerlink.com/content/p371t405258757r2/ (The Weighing of a Mechanical Gyroscope with Horizontal and Vertical Orientation of the Spin Axis by A. L. Dmitriev and V. S. Snegov That one costs money to read but this version from the Los Alamos archive is free but is by one of the authors and is reasonably factual. Measurements of the Influence of Acceleration and Temperature of Bodies on their Weight by A. L. Dmitriev http://arxiv.org/abs/0803.1730 "A brief review of experimental research of the influence of acceleration and temperatures of test mass upon gravitation force, executed between the 1990s and the beginning of 2000 is provided." On page 3: "At a speed of rotation of 18.6 thousand rev/min the relative reduction of weight of a rotor was equal to 3·10-6." A loss that small is in the class of "close to if not within experimental error", not comparable to a small boy lifting (one end?) of a rotating gyroscope. John http://tinyurl.com/6hl8h5 |
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