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From: Randy Poe on 29 Sep 2005 17:11 TomGee wrote: > No, sorry, Randy. Your eyes must be crossed. Tipler in my quote does > not equate the work done _to_ KE at all. I'm reading this message: http://groups.google.com/group/sci.math/msg/dd6f6945e97b7e6c in which you provided the following quote from Tipler: "The work done by an unbalanced force...on...[an object]...equals the change in the kinetic energy of the...[object]" > He specifically refers to the > work done on an object, yes, and says that it equals the change in KE of the object. > no on KE. How would you do work on KE, > anyways, since KE is the energy a body has due to its motion? How do you confuse sentences so thoroughly? The work is done by the force on the object. Work is energy. It is translated into kinetic energy of the object. Nowhere did I say, or Tipler say, that "work is done on the KE". However the quote you gave clearly says the work is EQUAL TO (not "done on") the change in KE, and I agree. How, on second reading of your own quote, did this get transmuted to "the force is equal to the KE"? Do you see the word "force" in that passage? - Randy
From: TomGee on 29 Sep 2005 17:12 Randy Poe wrote: > TomGee wrote: > > Randy Poe wrote: > > > TomGee wrote: > > > Yes, I keep talking about the relation between force and > > > momentum, whereas you keep correcting me that the topic > > > of discussion is the relation between force and momentum, > > > clearly a different thing. Sorry about that. > > > > > No, you keep talking about a derivative of momentum > > Because dp/dt = F is a derivative of momentum. > > > in a futile effort > > to show that momentum is not a force. > > Because dp/dt is not equal to p. > > Hey, that's my position, not yours! A derivative cannot be equal to the function from which it is derived! If you knew what a derivative is you would have known that. > > > > And you can't grasp what's wrong with that picture. > > Because your ignorance is impervious. > > > > And you've said "every physics textbook" does so, all over > > > the place. > > > > > Is that a fact or is that your opinion based on one of your far-out > > inferences? Cite the post so that I can check is you're lying or not. > > The exact quote was this: > > >> Sure "we" do, just read a physics book. It is rare where we don't > >> use terms like force and momentum nterchangably. > > So I read this as saying that you believe if I pick up any > physics textbook, I will find that force and momentum are > used interchangeably. It is rare that they do not. Therefore > it should be easy to find such a passage in any physics book. > > > > You can no doubt provide a quote from a physics > > > textbook where the term momentum is used to mean a force, > > > right? Thereby proving me wrong when I insist that nowhere > > > in physics is momentum used to mean "force"? > > > > > How would that show that "nowhere in physics" is it used that way? > > Read it again. "Nowhere in physics" is MY position. > > You show a real problem in comprehension of the written word. I know that is your position - did not say it was mine! Your low comprehension level shows that you don't understand English well enough to carry on a conversation without you requiring explanations of the meaning of almost every sentence. > > > Your > position is that it's rare for momentum and force NOT to be > used equivalently. Keep your position straight. > > And from that you came to believe that I think p and dp/dt are the same thing when I said they are not. Reading comprehension problem - to the woodpile for you. See if we can unscramble your brain. > > Finding such a passage in a physics textbook would prove > me wrong, because my claim is that such a passage doesn't > exist. Yours (do try to remember this) is that it does, and > such passages are common. > > Proved you wrong, didn't I? Gave you one but you still claim it does not prove you wrong. Which only proves nothing will prove you wrong. There is really no sense continuing this discussion with you, is there? > > > [Snip remaining rant. Same old story: Tom thinks p and dp/dt > are interchangeable]. > > No, you're the one who said that so you're the one who thinks that.
From: Randy Poe on 29 Sep 2005 17:15 TomGee wrote: > No, sorry, Randy. Your eyes must be crossed. Tipler in my quote does > not equate the work done _to_ KE at all. "The work done by an unbalanced force...on...[an object]...equals the change in the kinetic energy of the...[object]" Subject of sentence: work done on an object. Object of sentence: change in KE of object Verb: equals. You really don't think the passage above says the work done equals the change in KE? You don't see this sentence equating work and KE? You don't see "work" at the start, "KE" at the end, and "equals" in the middle? - Randy
From: Robert Low on 29 Sep 2005 17:30 TomGee wrote: > Hey, that's my position, not yours! A derivative cannot be equal to > the function from which it is derived! If you knew what a derivative > is you would have known that. What, not even when it's the exponential function?
From: Randy Poe on 29 Sep 2005 19:06
TomGee wrote: > Randy Poe wrote: > > Because dp/dt is not equal to p. > > > > > Hey, that's my position, not yours! A derivative cannot be equal to > the function from which it is derived! If that's your position, then can you explain this comment of yours? "False logic. dp/dt is a derivative of p so if force is a derivative of p, it must by definition also be p." http://groups.google.com/group/alt.sci.physics/msg/c61fe7149a24099a It sure looks to me like you're saying the derivative of p is also "by definition" p. Now as to this: > > >> Sure "we" do, just read a physics book. It is rare where we don't > > >> use terms like force and momentum nterchangably. > > > > So I read this as saying that you believe if I pick up any > > physics textbook, I will find that force and momentum are > > used interchangeably. It is rare that they do not. Therefore > > it should be easy to find such a passage in any physics book. > > You show a real problem in comprehension of the written word. I know > that is your position - did not say it was mine! Did you say "just read a physics book. It is rare where we don't use terms like force and momentum nterchangably."? Is your position that you did not say that? > > Finding such a passage in a physics textbook would prove > > me wrong, because my claim is that such a passage doesn't > > exist. Yours (do try to remember this) is that it does, and > > such passages are common. > > > Proved you wrong, didn't I? 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? > Gave you one but you still claim it does > not prove you wrong. Yes, I really can't see how "force is the time rate of change of momentum" proves F = dp/dt is wrong. Nor can I see how "work done on an object equals change in KE of the object" contradicts "force and momentum are not interchangeable". I really can't. - Randy |