Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site burl.UUCP Path: utzoo!linus!wivax!decvax!harpo!floyd!vax135!ariel!houti!hogpc!houxm!hocda!spanky!burl!rcj From: rcj@burl.UUCP Newsgroups: net.nlang Subject: Re: "change in displacement" Message-ID: <179@burl.UUCP> Date: Wed, 15-Jun-83 11:29:37 EDT Article-I.D.: burl.179 Posted: Wed Jun 15 11:29:37 1983 Date-Received: Thu, 16-Jun-83 16:39:44 EDT References: <467@ihuxr.UUCP> Organization: Western Electric, Burlington, NC Lines: 43 In reply to Lew Mammel's reply: a) I thought you guys were picky, but it turns out that you are not picky enough. I "quoted" Halliday and Resnick?????? Did uucp get smart all of a sudden and put quote-marks around that section of my article? The absence of quote-marks and the word quote in any shape, form, or fashion should have led you to the obvious conclusion that I was paraphrasing -- not quoting. I used the term "change in displacement", not H & R. b) In defense of "change of displacement", I give an example of the proper use of the phrase: If I start at the end of the hallway outside my office (initial position), and walk down the hall; at time 'a' I will have a displacement of 'x' feet (However far I was able to walk from time '0' to time 'a'. If I continue to walk, and again sample my position relative to my initial position at time 'b', I will find that I now have a displacement of 'y' feet. It is quite reasonable, at this point in my dramatic journey, to talk about the change in displacement which occured from time 'a' to time 'b'. It is also reasonable to talk about the average "change in displacement" from time 'a' to time 'b' as a function of time [average velocity]. If I go further still, and examine the "rate of change of change in displacement" (i.e., if it took me a time units to go x feet, and then it took me b-a time units to go y-x feet, then what was the change in my "change of displacement as a function of time" [velocity]), then I can define this as a crude measure of my "acceleration" during my walk. c) It is quite conceivable that 'x' above will have a greater magnitude than 'y' above -- because displacement is a vector quantity. If the hallway curves back on itself, then I might be closer to my initial position at time 'b' than I was at time 'a'. That is why speed and velocity do not equate, and why "rate of speed" and acceleration do not equate either. I will admit, however, that "rate of speed" and acceleration CAN equate IF it is understood that the directional component of velocity has no really tremendous effect on the problem (i.e. motion in a straight line only). And that is usually the common definition of speed. >From the asbestos keyboard,-- The MAD Programmer -- 919-228-3814 (Cornet 291) alias: Curtis Jackson ...![ floyd sb1 mhuxv ]!burl!rcj