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Re: MBL, was Re: Air resistance



At 11:12 AM 12/11/97 -0500, you wrote:
At 08:49 AM 12/11/97 -0500, Rick T. wrote:
(snip)
One experiment I try every
year is using a tilted air track to study accelerated motion and in part to
measure the acceleration due to gravity. This never works very well (the
technique requires a photo-gate to be triggered AS SOON AS the cart starts
to move down the incline and that is difficult to set up properly).

(snip)
I
thought that using a motion sensor, an air track, and a cart with a
reflector might be the answer. A couple of us set up the experiment, took
the data, and tried the analysis. What we got was GARBAGE. Ultimately we
recognized that we did have to average over longer time periods, but even
then the quality of the data was crap.

Motion detectors often don't work well with air tracks. The air turbulence
above the track interferes with the desired sound propagation.

We have used air tracks with motion detectors for years and have gotten good
results. In fact, the tilted air track experiment showing acceleration, and
conservation of energy has worked very well for us. We have even added a
spring so that the total energy is kinetic, plus gravitational potential,
plus spring mechanical energy, and have gotten very good results. By
setting the system into oscillation and watching the decay over a period of
time we have been able to get an estimate of the coefficient of friction
between the cart and the track.
__________________________________


Jim Riley
Department of Physics
Drury College
Springfield Missouri 65802
(417) 873 7233
e-mail: jriley@lib.drury.edu
fax: (417) 873 7432