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Re: speed and velocity



That (below) came out wrong!

I intended to point out the confusion between the average speed defined
as:

1) the average value of the magnitude of the velocity (equivalently, the
total distance traveled divided by the total elapsed time) and

2) the magnitude of the average velocity.

I think we should stick with the definitions: speed = ds/dt and velocity
= dr/dt, where s is scalar distance and r is vector displacement. This
makes speed the magnitude of the velocity and makes (1), above, the
definition of average speed. (2), above, goes un-named and is probably
not useful enough to have a name other than the "magnitude of the average
velocity".

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor

-----Original Message-----
From: Bob Sciamanda <trebor@velocity.net>
To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
Date: Monday, November 23, 1998 11:10 PM
Subject: Re: speed and velocity


-----Original Message-----
From: Brian McInnes <bmcinnes@PNC.COM.AU>
To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
Date: Monday, November 23, 1998 10:00 PM
Subject: speed and velocity

(1) 'Speed" is a handy word for "magnitude of velocity". In most
. . . Brian McInnes

A serious problem arises when speaking of average speed. The term
"average speed" can mean:

1) the average value of the magnitude of the velocity; or
2) the total distance traveled divided by the total elapsed time.

There are texts which define speed as the magnitude of the velocity and
then give problems asking for the "average speed", intending definition
(2) above.

-Bob

Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor