User talk:Brews ohare
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[edit] Happy First Day of Spring!
[edit] History of science section in centrifugal force
I've now started a section on the historical development of the modern conception of centrifugal force in that article. I am by no means an expert in the history of science, and I'm unsure about how the references I've cited hold together: I'd greatly appreciate it if you could please review the material I have added so far? There appears to be significant work on this topic by Domenico Bertoloni Meli (for example, [1], [2]), however, most of the interesting papers on this subject are behind a paywall and inaccessible to me. -- The Anome (talk) 12:30, 25 May 2008 (UTC)
[edit] Fictitious force wiki is wrong about planetary motion and Euler forces
Euler forces are tangential forces causing α = dω/dt? These don't go away in a constantly rotating frame-- they stay the same, since the acceleration of the particle is the same in either frame (just as in the linear case where acceleration is the same if you switch to a different inertial frame at a different linear velocity). Euler forces only appear as ficticious forces if you're in a frame with accelerated rotation rate where α = non-zero. But that's not the setup we carefully made for the centrifugal and Coriolis forces where ω is constant and dω/dt = α = 0. So in a way, the Euler forces are a different animal, and we really have to decide if we're going to stay fixed to a coordinate system or fixed on a rotating object which may not be rotating with a fixed rate. The planetary case is interesting: the Euler force is zero there, NOT because of the fact that the revolution rate doesn't change (as it states falsely in the fictious force Wiki)-- because the revolution rate of a planet DOES change for eliptical orbits! Instead, Mr. Tombe's "law of areal velocity" per Kepler kicks in (a consequence of angular momentum preservation) which causes r to decrease as ω increases, so the product stays constant and thus the Euler term stays zero even IF dω/dt is not zero: this is perhaps what confused Mr. Tombe (he as thinking about Euler forces and calling them Coriolis forces; most of what he said about one was true for the other!). Euler force = 0 even with variable rotation, and this happens any time the force is purely central, as with planets and no drag, or (say) when a skater pulls in her arms, etc. All again because of conservation of angular momentum in a system with no external angular momentum-changing influences. SBHarris 21:01, 30 May 2008 (UTC)
- Steven: I find your remarks confusing. Marsden provides a formula for the Euler force for a rotating frame as m r × dω / dt, which certainly vanishes for a constant rate of rotation, not supporting your lead sentence. Then a sentence or so later, you seem to agree with this remark. What are you trying to say here? Brews ohare (talk) 15:48, 31 May 2008 (UTC)
[edit] Articles about Dynamics
I've noticed that you are working a lot on the Kinematics article. A few months ago I compiled a list of all (maybe there are more) articles related to Dynamics. This list is located in the talk page of the Dynamics article. I thought this list would be useful for you if you are planning on working on more articles related to Kinematics. Some of those articles need to be merged. I would like to work on some of these articles but my focus right now is on other topics. Cheers!!! Sanpaz (talk) 23:53, 4 June 2008 (UTC)
