lew@ihuxr.UUCP (06/13/83)
Curtis Jackson threw gas, not water on my "rate of speed" fire. He quoted the phrase "change in displacement" from Halliday & Resnick. Displacement is a change in position. Webster's gives "the difference between the initial position of a body and any later position" as one definition. I find "change in displacement" much more offensive than "rate of speed". Considering that it occurs in an important definition in an authoritative text, I'm absolutely aghast. I think you will find in general that educators are equally as capable of linguistic and logical atrocities as are small town cops. Lew Mammel, Jr. ihuxr!lew
rcj@burl.UUCP (06/15/83)
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