[Phys-L] Re: coefficient of friction or drag

[anngeorg at PACBELL.NET (Bernard Cleyet)]

Pete!

Among your students may be one (one would hope more than one) who would
enjoy learning about turbulent drag.  There is a wealth of www sites
that discuss this, both qualitatively and mathematically both accessibly
and well beyond most HS students.  One site discusses the results from
coffee filters experiments using a sonic ranger.  Both Eisberg (and
Lerner) and Feynman et al discuss, qualitatively and mathematically,
viscous and turbulent drag and the Reynolds number in a HS accessible
manner (partly).  E. and L.  discuss in detail a numerical simulation of
the skydiver, it doesn't even require calculus, tho it is a form of
calculus.

bc, whose education passed over all this, but learned it when a friend
claimed a pendulum undergoing significant drag had an unchanged period.

P.s. Just before discussing the skydiver, E. & L. discuss mathematically
the rocket problem as an example of variable acceleration.  The sky
diver is their second example wherein the drag varies instead of the
mass leading to varying acceleration.

Pete Lohstreter wrote:

> Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Thursday,
> December 23, 2004 at 8:13 AM -0600 wrote:
>
>
> > I am planning to conduct a model rocket project with a high school physics
> > class and I wanted them to collect data on their rockets.
> > One of the variables that I wanted them to determine is the coefficient of
> > friction or drag on the parachute as the rocket came back down.
> > I wanted to get an opinion on the best way to accomplish this.
> > My first thought was to have them find the velocity of the rocket on its
> > descent and calculate the velocity of the rocket where there is no
> > friction.
> > Then use the frictionless rocket as the accepted value and the velocity
> > they
> > found for their descent as the experimental value.
> > (Accepted value minus experimental value)/ accepted value.   The
> > difference
> > in the velocities is due to friction or drag.
> >
> >
> > What might be a better way?
> > They will know the beginning mass, ending mass, altitude, and time of
> > flight
> > both up and down.
>
> http://www.pcprg.com/rounddes.htm
> Try this.  It might help...
>
> Pete Lohstreter                         "Happy is he who gets to know
> The Hockaday School               the reasons for things. "
> 11600 Welch Rd                        Virgil (70-19 BCE) Roman poet.
> Dallas, TX  75229
>
> 214-360-6389
>
> plohstreter@mail.hockaday.org
>
>
>
> See what our students are doing......
> http://home.hockaday.org/HockadayNet/Academic/physics/index.html