PAllen's latest activity
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PPAllen replied to the thread Undergrad KE of rotating disc.I am simply describing a procedure to arrive at the final state starting from a rest state.
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PPAllen replied to the thread Undergrad KE of rotating disc.The proposed integral in the OP impies the following physical process: a disc of dust with uniform density in some inertial frame is...
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PPAllen replied to the thread Undergrad KE of rotating disc.I claim the integral in the OP, evaluated between specified r values below R corresponding to speed c, will always be finite, and no...
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PThere is one more way to look at the problem, to avoid the continuum distribution of matter in the radial direction. Consider ##N##...
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PPAllen replied to the thread Undergrad KE of rotating disc.I don't believe this is correct, and you haven't made any attempt to demonstrate this part. The calculation for such an annulus with...
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PPAllen replied to the thread Undergrad KE of rotating disc.I think the implication is a similar phenomenon - the circumference of the rim grow unbounded, but this leads only to limiting area of 2...
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PPAllen replied to the thread Undergrad KE of rotating disc.So, if you do just treat the rim as one dimensional, with a linear mass distribution per the COM frame, you do get KE unbounded in the...
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PPAllen replied to the thread Undergrad KE of rotating disc.Qualitatively, what I am getting at is that as the rim speed approaches c, the number of small area elements of given measure (per a...
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PPAllen replied to the thread Undergrad KE of rotating disc.I think the cause is that the mass distribution is specified in the inertial frame. Then, in the local frame of a rotating piece, as the...
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PPAllen replied to the thread Graduate Feynman's bug (hot plate) in generality.Getting back to the original question, rephrased as: can the intrinsic geometry of a topologically trivial piece of a general Lorentzian...
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PPAllen replied to the thread Graduate Topological constrains for the solutions of EFE.To me, the idea is that formalizing the notion of global isotropy and homogeneity leads to both topological constraints and geometric...
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PPAllen replied to the thread Graduate Topological constrains for the solutions of EFE.It seems to me that global homogeneity and isotropy, formalized as requiring the product of R and a maximally symmetric, homeneous...
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PPAllen replied to the thread High School Potato paradox.I have bumped into problems that are trivial given the assumption that there is a well defined answer, but more tedious if you don't...
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PPAllen reacted to Nugatory's post in the thread Undergrad How many sorts of time are there in physics? with
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In general, no. We can choose any coordinate system we please according to whatever amuses us, and there's no reason that the...