Motion
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From: TomGee on 5 Oct 2005 03:39 It is you who is well-known for not supporting your own wild opinions. When I give you a reference in reply to your promise that it will suffice, and you accept it, you still welsh on your promise anyway. Here's what PD on 09/16/05 - 2:19pm in the topic asking what keeps an electron going, etc., in response to "Too Many Kooks..." question below. > How can a planet rotate permanently without energy supply? After all, > it's accelerating non-stop. > That's what gets me. "Which is proof that acceleration does not amount to a change in kinetic energy. (Who said that it was?)" PD
From: TomGee on 5 Oct 2005 03:59 Now here, Poe, is what you said up above: > > And finally I guess you'd say that a body with KE will maintain > > a constant velocity forever if there are no external forces. > > And again I'd agree: if there are no external forces, KE > > is conserved, and so motion is unchanged. > Oh, wonderful. I am surprised, but elated too at having been able to > get my point across to you. However, I would not say the constant > velocity can be maintained forever. I see nothing about circular motion here.
From: PD on 5 Oct 2005 07:41 TomGee wrote: > It is you who is well-known for not supporting your own wild opinions. > When I give you a reference in reply to your promise that it will > suffice, and you accept it, you still welsh on your promise anyway. > > Here's what PD on 09/16/05 - 2:19pm in the topic asking what keeps an > electron going, etc., in response to "Too Many Kooks..." question > below. > > > How can a planet rotate permanently without energy supply? After all, > > it's accelerating non-stop. > > > That's what gets me. > > "Which is proof that acceleration does not amount to a change in > kinetic > energy. (Who said that it was?)" > > PD That's right. Circular motion is a case where there is acceleration present and no change in kinetic energy. You have taken my statement to mean that there is *never* a case where acceleration produces a change in kinetic energy. I did not say that. What I said was that the presence of acceleration does not necessarily imply a change in kinetic energy, which was the poster's point of confusion. PD
From: Randy Poe on 5 Oct 2005 09:43 TomGee wrote: > Now here, Poe, is what you said up above: > > > > And finally I guess you'd say that a body with KE will maintain > > > a constant velocity forever if there are no external forces. > > > And again I'd agree: if there are no external forces, KE > > > is conserved, and so motion is unchanged. > > > Oh, wonderful. I am surprised, but elated too at having been able to > > get my point across to you. However, I would not say the constant > > velocity can be maintained forever. > > I see nothing about circular motion here. That's because circular motion is not an example of the absence of external forces. You have claimed that both PD and I made a general statement that in the PRESENCE OF FORCES, acceleration does not change KE. In the absence of external forces, there's no acceleration which by definition means velocity and KE are constant. - Randy
From: TomGee on 5 Oct 2005 09:45
No, PD, you said no such things. You only wish now that you had said such things. Hindsight is a wonderful thing but it too often comes too late. (Tomgee) |