At 5:53 PM -0500 1/14/02, JIMRPT@AOL.COM wrote: >In a message dated 14/01/02 4:50:14 PM, JD@Pianomaker.co.uk writes: > ><<"OF COURSE a body can experience a change in velocity without moving >bodily. If this did not happen, there would be no such thing as >vibration.">> > >Uhh JD...the definition of "vibration as relates to physics is: > >vibration (n) >........... >"2. Physics. a. A rapid linear motion of a particle or of an elastic solid >about an equilibrium position. b. A periodic process. >3. A single complete vibrating motion; a quiver." AHD Webster gives: "a periodic motion of the particles of an elastic body or medium in alternately opposite directions from the position of equilibrium when that equilibrium has been disturbed..." When a shock or sound wave travels from one end of a rod to the other, the rod does not move and the particles of the rod will move at different times in different directions within a very limited range. > >and for "velocity it is: >velocity (n) >.......... >2. Abbr. V. Physics: A vector quantity whose magnitude is a body's speed and >whose direction is the body's direction of motion. AHD That is a very partial definition. Even Webster does better: 2a time rate of linear motion in a given direction : a vector quantity equal to speed in a particular direction and relative to a _stated_frame_of_reference. Note that the word "body" is not specified. A particle within a body may have velocity and in fact always does except at absolute zero. What AHD is, I don't know, but it strikes me that Webster, just an ordinary dictionary, has taken a lot more trouble to define the words. A fuller definition of "vibration" would need to distinguish between 'free vibration', 'damped vibration' and 'forced vibration', and then some quite complicated mathematics would need to be adduced to describe and quantify these phenomena. I really see no point in these trite little points. If you and others want to reduce the problem to the batting about of half-baked "definitions" and presume that it's all simple obvious stuff, then you may satisfy yourselves that you know all there is to know, but you won't add anything to our knowledge of the subject. Frankly I'm sick and tired of the petty ignorant level this discussion is constantly reduced to by people who really seem to think they have nothing to learn. I have a lot to learn and there are others who also wish to further their knowledge of this extremely complicated question, and I don't appreciate having to waste my time in some damn stupid fencing match with people who are only interested in scoring points because they're too lazy or ignorant to lay aside their preconceptions and do some proper thinking. JD
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