Horace Heffner wrote: > > On Feb 6, 2006, at 11:10 AM, Harry Veeder wrote: > >> I am interested in how gravimagnetic theory may pertain to the motion >> of a curling stone. >> >> When a curling stone is slowly rotating as well as sliding the path of >> motion tends to "curl" in the direction of rotation. Why this happens >> remains very controversial but each explanation advanced assumes >> a unique model of the frictional forces involved. >> >> Since gravimagentism is isomorphic with electromagnetism, then >> then the appearance of a gravimagentic field depends on the relative >> acceleration or deceleration of the masses. >> >> In regards to a stationary Earth, the sliding motion (deceleration) >> of a >> curling stone over the Earth generates a relatively weak gravimagnetic >> field. However if the curling stone is regarded as stationary and >> the Earth >> as sliding under the curling stone, then the deceleration of the >> Earth will >> generate a relatively intense gravimagnetic field. >> >> Add a little rotation to the mix and I have a hunch that the "curl" of >> curling stone can be explained by gravimagnetism. >> >> What do you think? >> >> Harry > > I don't think gravimagnetism has anything to do with it. The > gravimagnetic forces involved here are way too small. > > There are (at least) a couple existing theories. See: > > <http://www.timesonline.co.uk/article/0,,2090-1325839,00.html> > > On first glance, Shegelski's theory looks like it makes more sense > than Marmo's, but you can't discount practical knowledge. It seems > to me some fairly simple experiments could figure out the truth. > > One reason Marmo's theory looks bad is that forces directed > longitudinally to the sides simply tend to make an object spin, not > laterally accelerate. There is no significant Bernoulli principle > involvement as there is with baseballs, etc. > > My first impulse, having no practical experience with curling at all, > is to suggest the sheer force between the ice and the stone at the > back is greater than the similar sheer force at the front of the > stone. Thus a net right directing force exists on a moving and > clockwise turning stone. When the added ice and water burden is > brushed from the ice, the front end of the stone lowers, the water > surface width decreases, and the shear force increases. > > Marmo states: "My theory is quite simple compared to theirs, which > doesn't explain why there is much more water at the front than the > back ?". > > I would think a correct theory would tend to make use of this fact > more than explain it. The more water up front, the less the sheer > force of the water on the front of the stone. To increase the > leftward force on the front of the stone, and thus balance the > rightward force at the back, it is only necessary to reduce the > amount of water and meltable ice the stone runs over and thus drop > the front of the stone so it runs on a thinner layer of water. When > the front end of the stone rides on the same amount of water as the > back the shear forces are balanced and the stone goes straight. > > That's my guess. Only good data can tell for sure. > > Horace Heffner. >
Thank you for spending the time to familiarise yourself with the issues. My interest in the subject began several years ago and I have read many papers on the subject. (Those that have been published in the Canadian Journal of Physics can be downloaded for free.) I am not satisfied with the explanations that postulate differential frictional forces. At first blush if they are true the amount of curl should increase with the rotation rate, and this is simply not observed. Of course it is possible to postulate an elaborate system of friction so that the mathematics will replicate the observed motion but this approach IMO is like the use of epicycles to explain orbital motion. Harry
