Re: acceleration

[Matt Jusinski <mjusinski@YAHOO.COM>]

> In my book, there is such a thing as scalar
> acceleration
> which means an increase in speed (|v|).  It is the
> opposite of deceleration.  This meaning of the word
> has been around for centuries and cannot be
> considered
> wrong.  Every physicist I know uses the word in this
> way some of the time.
>
> Of course there is also such a thing as vector
> acceleration
> which is the quantity that appears in F=ma.
>
> Asking what is "the" acceleration at the peak of a
> parabolic arc is at best ambiguous.
>   -- The scalar acceleration is zero.  The speed
> is locally constant at this point.

If the scalar acceleration is zero locally, and the
speed is locally zero, Why does a projectile fall back
down?

It seems to me that scalar acceleration is not much
help in explaining most common phenomenon.


Matt Jusinski  Morris Hills Regional District



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