Motion
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From: Randy Poe on 4 Oct 2005 10:02 Don1 wrote: > Randy Poe wrote: > > Randy Poe wrote: > > > TomGee wrote: > > > > Aren't you the one who said KE is not changed by an external force? > > > > > > No, I never said such a thing. Can you provide the quote where > > > you garbled that inference from? > > > > > > > I think I can save you some work. I said that in the case of > > circular motion, the force does not do any work on the object, > > and it also does not change the KE. > > > Are you saying that a force acting at right angles to a moving body is > not doing any work. I'm saying that work is done by the component of force in the direction of motion. If the force is ALWAYS at right angles to the motion, no work is done. > or changing the Kinetic energy as it changes the > directin? I find this hard to believe. KE = 0.5*mv^2 If v doesn't change, KE doesn't change. Do you think that the speed ever changes for constant-speed circular motion? > I think we need to study this > situation with a fine tooth comb. There's nothing to study. - Randy
From: Randy Poe on 4 Oct 2005 10:11 Don1 wrote: > Your quote of middle school science books constitutes positive proof in > your mind, and might even stand up in a court of law, but it's a crock. Is arithmetic a crock because it is taught at young ages rather than in college? > When a force acts at right angles to a moving body, the body is turned, > and curves away from the force; not instantaneously but proportional to > the magnitude of the force and it's duration. If the body responded > instantaneously there would be an inward jump instead of a curve, and a > ratchet effect would result. > > Instead, the force displaces the moving body, resulting in elliptical > curvature. So your position is that circular motion is impossible? - Randy
From: Don1 on 4 Oct 2005 10:33 Randy Poe wrote: > Don1 wrote: > > Your quote of middle school science books constitutes positive proof in > > your mind, and might even stand up in a court of law, but it's a crock. > > Is arithmetic a crock because it is taught at young ages > rather than in college? > > > When a force acts at right angles to a moving body, the body is turned, > > and curves away from the force; not instantaneously but proportional to > > the magnitude of the force and it's duration. If the body responded > > instantaneously there would be an inward jump instead of a curve, and a > > ratchet effect would result. > > > > Instead, the force displaces the moving body, resulting in elliptical > > curvature. > > So your position is that circular motion is impossible? > > - Randy No; circular motion _is elliptical_; with a constant radius all around.
From: TomGee on 4 Oct 2005 17:28 Randy Poe wrote: > TomGee wrote: > > Randy Poe wrote: > > > In my universe, if two things are the same by definition, > > > they're equal. > > > > > > > > Yes, but in the real universe, they're not always equal. > > In the real universe, things that are the same are always equal. > > How would you know that living in your own universe where Relativity is reality and reality is fantasy? So now you propose to eliminate one of those two terms since one is now redundant in your universe? "Same" is a word "indicating that one thing or person is involved rather than two or more different things or people", and "equal" means "identical in size, quantity, value, or standard". Microsoft® Encarta® Reference Library 2005. © 1993-2004 Microsoft Corporation. All rights reserved. At that level of understanding, there is no equivalence between the two, but if you are correct, at some other level, they are equal in meaning. Just like at some level other than at the core-definition level, words are commonly used interchangably where the core meanings are not in conflict with the context. The core meanings of energy and force are not equal, and neither is momentum, but above their core meanings, they are often validly used as being one and the same thing. But you're wrong in saying that things that are the same are always equal. You might mean they are equivalent, but in your universe where words have no meaning other than their core-definitions, that is impossible because you cut no slack in word usage at all. So you're contradicting yourself when you say that. > > > > What objects > > or quantities or properties are equal to depends on more than just an > > equal sign. If you say, "These two mountains are equal", the statement > > is nonsense. > > But so is the sentence "those two mountains are the same." > > Yes, thank you. > > > > For it to make sense, you must qualify it something to > > compare the two, height, area, mineral amounts, difficulty in climbing, > > etc. > > If I were to say "the heights of those two mountains are them > same" I would also mean "the heights of those two mountains are > equal". Ditto for difficulty, mineral content, or surface area. > I can't imagine a situation where I would use "same" but also > mean "not equal". > > Why don't you say that, then, instead of nonsensically saying, "Those two mountains are the same"? > > > > > That makes no sense. Again, if two things are the same thing, > > > they're equal. > > > > > Yes, in your universe. > > OK, having rejected logic, you now reject A = A. > > Well, that may seem logical to you but it's a tautology and thus, redundant, to say the least, and nonsense, to say the most about it. > > > > > > > By the Tipler quote that says force is the time rate of change > > > > > of momentum? > > > > > > > > > > Again, how does that prove that F = dp/dt is wrong? > > > > > > > > > > > > > > Another one of your bad inferences. > > > > > > Tipler said that force is the time rate of change of momentum. > > > That's not an "inference", it's in the quote you provided. > > > > > > Above, you claim the Tipler quote proves me wrong. > > > > > In your universe, proving you wrong equals proving F=dp/dt wrong, so > > that's why you inferred I said that. > > What else are we arguing about? What do you think the Tipler quote > proves me wrong ABOUT? I see nothing in the Tipler quote to > disagree with. > > Yes, you've said that before and I tried to explain it to you. Now, I've forgotten what it was I said about it. > > > > > Well, I did, actually. It's true in non-relativistic situations, > > > but not in general. > > > > > But in your universe relativistic situations are reality while in our > > real universe, relativistic situations are imaginary. Not only are > > your eyes crossed, but your brain is upside down. > > No comment. Every one of your pronouncements is a gem. > > Thank you. They don't come easy to me. > > > > > > > Nor can I see how "work done on an object equals change in > > > > > KE of the object" contradicts "force and momentum are not > > > > > interchangeable". > > > > > > > > > Aren't you the one who said KE is not changed by an external force? > > > > > > No, I never said such a thing. Can you provide the quote where > > > you garbled that inference from? > > Can you? > > I took time to find it and it turns out it was your pal PD who said that. You've said a bunch of other silly things but it was not that one. So I guess I have to fool with your silly question. Hmmm. I see no contradiction above either, so that means you made something up again (another one of your famous inferences).
From: PD on 4 Oct 2005 18:19
TomGee wrote: > Randy Poe wrote: > > TomGee wrote: [snip] > > > > > Aren't you the one who said KE is not changed by an external force? > > > > > > > > No, I never said such a thing. Can you provide the quote where > > > > you garbled that inference from? > > > > Can you? > > > > > I took time to find it and it turns out it was your pal PD who said > that. And it was absolutely correct in the context of circular motion where you last saw it. PD > You've said a bunch of other silly things but it was not that > one. So I guess I have to fool with your silly question. Hmmm. I see > no contradiction above either, so that means you made something up > again (another one of your famous inferences). |