[Phys-L] Re: Average earlier or average later?

[rlamont <rlamont@POSTOFFICE.PROVIDENCE.EDU>]

I think Bob's approach makes the most sense. It is the one that I
take with my students in lab. To me, you average the quantity you
are interested in as your final result. If I have a distribution
of distances and times, I would calculate the individual speeds
from the raw data and then look at the distribution of the
results - average, standard deviation, etc.

As someone mentioned, the average of the times is not useful in
finding the average of the reciprocal times.

Bob at PC

> -----Original Message-----
> From: Forum for Physics Educators [mailto:PHYS-
> L@list1.ucc.nau.edu] On Behalf Of Bob Sciamanda
> Sent: Friday, September 09, 2005 11:37 AM
> To: PHYS-L@LISTS.NAU.EDU
> Subject: Re: Average earlier or average later?
>
> Which average you use depends on what you are going to do with
it:
> For instance, the conclusion that the average energy of a
monatomic
> ideal
> gas is 3kT/2 requires the average of (mv^2)/2, not the energy
of the
> molecule with the average speed.  IE. the conclusion uses the
average
> of the
> squared speed, not the square of the average speed (in
specifying the
> average energy).
>
> Bob Sciamanda
> Physics, Edinboro Univ of PA (Em)
> http://www.winbeam.com/~trebor/
> trebor@winbeam.com
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