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From: TomGee on 10 Oct 2005 11:11 Randy Poe wrote: > TomGee wrote: > > Randy Poe wrote: > > > TomGee wrote: > > > > Randy Poe wrote: > > > > > > I said this: > > > > > 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. > > > > > > And Tom, apparently in reply, said this: > > > > > > > Ah yes, so then work is being done by the component of force which you > > > > claim is a non-existent force? > > > > > > I can't connect this to what I said since I said nothing about > > > (a) work being done (I was explicitly talking about work NOT > > > being done) and > > > (b) a non-existent force. > > > > > > > > Yes, you did: (a)"I'm saying that work is done by the component of > > force in the direction of motion" In English that means _when and if > > ever_ work is done, it is then being done by the "force" > > That's correct. And it's being done by the component of > force which is in the direction of motion. > > > which you mentioned but failed to name. > > Eh? It's a general statement. When work is being done, it's > being done by the component of force in the direction of > the motion. What "name" is missing there? > > Oh you're sooo coy! > > > > It's clear that you were talking about a > > force that does work in a body's "direction of motion" > > Yes, when work is being done. > > > in support of your statement that no work is being done by > > the right angle force on an orbiting object > > Right, no work is being done in that case. > > > wrt its KE. > > That's meaningless. What does "work wrt its KE" mean? > > More coyness! You said that the KE of an object does not change under the right angle force because under that force no work is being done, and we all agree with that. You then supported that statement by saying that some other force does work moving a body in its "direction of motion". > > > > That is correct of course but you did not think it through well enough > > to notice that your unnamed "...component of force in the direction of > > motion" is the (b)"non-existent" force which you et al claim is not > > needed by sole objects having zero net external forces to move at CV. > > That's right, I didn't think that there is a component of > force in the case of zero force > > Well, duuuh! Yes, you didn't think.... Now that you have thought it over a bit, don't you think that means there is a force in the case of nonzero force? > > > When the force is zero, all components are zero. > > What components are those? The FM Stereo tuner? The amp? Subwoofer? You don't have to keeping that same statement over and over anymore, you have said it enough times to where we are convinced you understand that zero means zero. > > > When no work is being done, as in the case of constant > velocity, there are no external forces present. > > Wrooonnnnggggg! There is no work being done on the object by any NET external forces. Only in the case of CV can we say there are no net external forces acting on the object. > > > When there are no external forces, there is no work being > done, and KE is constant. > > Reference, please. > > > > > > What force makes the work in moving the body? > > > > > > There is no "work" being done in moving a body at constant > > > velocity in the absence of any external forces. > > > > > But you said above that work is done by "the component of force in the > > direction of motion". > > Yes, and in the case of constant velocity, there is no > force. > > But that contradicts your statement that work is done by a force in the direction of motion because CV has a direction of motion to it! As I've said, you can't have it both ways, and there ain't no free lunch! Give it up before someone says something to hurt your feelings! > > > > What force are you talking about? > > The force that is present when work is being done, > KE is changing, and velocity is changing. None of which is > true in the case of constant velocity. > > But what about the force doing work in the direction of motion? You failed to qualify the direction so that means an object has a force moving it in any direction, whether or not it's constant. > > > > You're afraid that naming it will cause you to lose this > > debate, aren't you? > > No, I can name the force in the case of constant velocity: > it is called "zero". > > Wrrooonnnnggggg!
From: TomGee on 10 Oct 2005 11:23 Randy Poe wrote: > TomGee wrote: > > > Please point me to a place where Newton's Laws or Conservation > > > of Energy fails to describe the system correctly. > > > > > > > > Gee, I don't know - the space-time continuum? > > Been watching Star Trek? Picked up a new vocabulary word? > > Oh that's so funny. > > > The "space-time continuum" is where we live and use Newton's > Laws every day. NASA uses them to plot trajectories to very > high precision. > > AE's s-t continuum is a math construct and as such it is an imaginary place! But you go on believing it's where you live (because it probably is), and if you find a way to use Newton's laws in your imaginary universe, well, let us know about it will you? > > > You probably meant to say something clever about relativity, > but you're wrong. > > I meant no such thing, so it is you who is wrong again. > > > In the absence of forces, particles > still follow straight lines (now called geodesics), > force is still equal to dp/dt, and momentum is still > conserved. > > Did someone ring your bell? If not, then you're beginning to blurt out kneejerk responses even without any codewords!
From: Torkel Franzen on 10 Oct 2005 11:26 "Randy Poe" <poespam-trap(a)yahoo.com> writes: > > Gee, I don't know - the space-time continuum? > > Been watching Star Trek? Picked up a new vocabulary word? "The spacetime continuum" is Back to the future-language, not Star Trek language.
From: Randy Poe on 10 Oct 2005 11:34 TomGee wrote: > Randy Poe wrote: > > TomGee wrote: > > > Randy Poe wrote: > > > > TomGee wrote: > > > > > Randy Poe wrote: > > > > > > > > I said this: > > > > > > 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. > > > > > > > > And Tom, apparently in reply, said this: > > > > > > > > > Ah yes, so then work is being done by the component of force which you > > > > > claim is a non-existent force? > > > > > > > > I can't connect this to what I said since I said nothing about > > > > (a) work being done (I was explicitly talking about work NOT > > > > being done) and > > > > (b) a non-existent force. > > > > > > > > > > > Yes, you did: (a)"I'm saying that work is done by the component of > > > force in the direction of motion" In English that means _when and if > > > ever_ work is done, it is then being done by the "force" > > > > That's correct. And it's being done by the component of > > force which is in the direction of motion. > > > > > which you mentioned but failed to name. > > > > Eh? It's a general statement. When work is being done, it's > > being done by the component of force in the direction of > > the motion. What "name" is missing there? > > > > > Oh you're sooo coy! No coyness, you're just confused. There are three separate situations we're talking about, and you keep taking words I say from one and applying them to another. I'm not being "coy" when I try to put those words back where they were said. The situations are: (a) No external forces. Velocity and KE are constant. There is no force to do any work, so discussions of "work" are meaningless. (b) External force present, but at right angles to the motion (e.g. circular motion). Here there is a force which could do work, but the geometry is such that no work is done. Speed and KE are constant. Velocity is not, in the sense that direction changes. (c) External force present, not at right angles to the motion. Now the force is doing work. Speed and KE are changing. If the force does 1 Joule of work, the KE changes by 1 Joule unless there are losses (due to friction). But at any rate the KE can't change unless the force does work to change it. > > Right, no work is being done in that case. > > > > > wrt its KE. > > > > That's meaningless. What does "work wrt its KE" mean? > > > > > More coyness! What's "coy?". "Work wrt KE" is an abuse of the language. It doesn't mean anything. > You said that the KE of an object does not change under > the right angle force because under that force no work is being done, > and we all agree with that. Good. This is situation (b) > You then supported that statement by > saying that some other force does work moving a body in its "direction > of motion". Not in situation (b). I said that in contrast to this situation, there is a *different* situation which I'm now calling (c). > > > That is correct of course but you did not think it through well enough > > > to notice that your unnamed "...component of force in the direction of > > > motion" is the (b)"non-existent" force which you et al claim is not > > > needed by sole objects having zero net external forces to move at CV. > > > > That's right, I didn't think that there is a component of > > force in the case of zero force > > > Well, duuuh! Yes, you didn't think.... And I still don't think that I have to talk about "unnamed components of force" in situations where the force is zero. Obviously you think that when there are no forces, there's a force to talk about anyway. OK, please describe to me the external nonzero forces in the situation where the external forces are zero. > Now that you have thought it over a bit, don't you think that means > there is a force in the case of nonzero force? Yes, but you will notice that when I said "I didn't think that there is a component of force in the case of zero force" I was referring to the case of ZERO force. That's different from NONZERO. See the difference? ZERO... NONZERO. They mean different things. > > When the force is zero, all components are zero. > > > What components are those? The components in any direction. If I have zero force, I can also say I have zero horizontal force, zero vertical force, zero upward force, zero northward force, zero eastward force... Do you disagree? > You don't have to keeping that same statement over and over anymore, > you have said it enough times to where we are convinced you understand > that zero means zero. Good. Yet you claim there is a force present in the case of no external forces. > > When no work is being done, as in the case of constant > > velocity, there are no external forces present. > > > Wrooonnnnggggg! There is no work being done on the object by any NET > external forces. Only in the case of CV can we say there are no net > external forces acting on the object. I just said that. > > When there are no external forces, there is no work being > > done, and KE is constant. > > > Reference, please. It's in the Tipler quote you provided. > > > > > What force makes the work in moving the body? > > > > > > > > There is no "work" being done in moving a body at constant > > > > velocity in the absence of any external forces. > > > > > > > But you said above that work is done by "the component of force in the > > > direction of motion". > > > > Yes, and in the case of constant velocity, there is no > > force. > > > But that contradicts your statement that work is done by a force in the > direction of motion because CV has a direction of motion to it! Mixing of situations (a) and (c). When a force is present, work is done by the force in the direction of motion. When a force is not present, there is no force "in the direction of motion" or in any other direction. When I say "work is done by the component of force in the direction of motion", I am not saying "when there's motion there's a force in that direction". I'm saying "when there's a force and it's in the direction of motion, it's doing work." - Randy
From: stephen on 10 Oct 2005 11:40
In sci.math Torkel Franzen <torkel(a)sm.luth.se> wrote: > "Randy Poe" <poespam-trap(a)yahoo.com> writes: >> > Gee, I don't know - the space-time continuum? >> >> Been watching Star Trek? Picked up a new vocabulary word? > "The spacetime continuum" is Back to the future-language, not > Star Trek language. Ford Prefect: "Eddies in the space time continuum" Arthur Dent: "Ah, is he. Is he." Stephen |