Re: dimensionless units & Mach Number

[Arlyn DeBruyckere <ARLYND@HUTCH.K12.MN.US>]

Most of my students are not familiar with the idea of a Mach number.  I
still use examples like this because it helps some of the students but I
must constantly remind myself that I need to do more to "reach" others.
Like Dr. Rauber, when I was in high school most everyone had a common
base experience that teachers could use as examples.  I find that today
very few students have this common base - many have never opened the
hood of a car much less worked on one, many do not play sports so they
do not have a "feeling" for related projectile motion, etc.  This means
that I must spend class time giving them a common experience with an
activity - a "lab".  Even then I must often point out observations that
I think are obvious but they think are very subtle.

Joel Rauber wrote:
>

> My suggestion (never tried by me) was predicated on the idea that Mach
> number might be less obscure than radians to students.  Perhaps it is
> showing my age by thinking that!  When I was a kid (60's and early 70's)
> most of the kids in middle school (at least the boys) had a real good idea
> of Mach number.  I suspect my older siblings who were young in the 50's also
> had a good idea.
>
> Some of you high school teachers on Phys-L, what is your impression of the
> state of awareness of Mach number in your students?

> Joel Rauber
> Joel_Rauber@sdstate.edu

--
Arlyn DeBruyckere
Hutchinson High School
1200 Roberts Road SW
Hutchinson, MN 55350
http://www.hutch.k12.mn.us/