Re: speed and velocity

[Phil Parker <PPARKER@TWSUVM.UC.TWSU.EDU>]

> Date:    Thu, 26 Nov 1998 17:53:06 +1100
> From:    Brian McInnes <bmcinnes@PNC.COM.AU>
>
> Bob Sciamanda sent three interesting e-mails to the list earlier today.
>
> I have a problem with his definition of a one-dimensional vector as a
> component of a three-dimensional vector, carrying a sign for direction.
>
> As I understand it a component is obtained by a vector dot product and is a
> scalar, not a vector.  the sign is not the direction of a vector but a
> consequence of whether the angle involved in obtaining the component is less
> or greater than pi/2.  In particular, vectors do not have signs, they have
> directions; they are intrinsically positive.
> What we can do (and this was the line that Tim Folkerts took as along) is to
> associate the components with a unit vector along the special one-dimension
> line.
In mathematics we distinguish between scalar components and vector
components for precisely this reason.  We would say Bob mentioned vector
components, and you've described scalar components.
   Also in mathematics, vectors can have signs, but the sign attached to a
vector is conceptually different from the sign attached to a number. Using
the same minus symbol for both is a bad idea from a purely conceptual view,
but it's very human.

---------------------------------------------
Phil Parker        pparker@twsuvm.uc.twsu.edu
Random quote for this second:
  Really? What a coincidence, I'm shallow too!