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Cindy Schwarz TPT editorial, was free fall data



On 16 Sep 1997 John Gastineau <gastineau@mindspring.com> wrote:

Did anyone see the commentary that Cindy Schwarz wrote for the TPT
that just arrived? Great food for thought. I won't comment just yet
on the contents, but call everyone's attention to it. The discussion
will continue, I'm sure.

Here is the virtual reality approach to free fall data. Using Interactive
Physics I first asked for seven digits to be displayed. The data produced
by the program are shown in the first two columns. You can verify them
with y=0.5*g*t^2 (using g=9.806650). The differences in y lead to v, and
differences in v lead to four consecutive values of g. Nearly identical!

t y v g

0 0
0.1 0.04903325 0.490332
0.2 0.1961330 1.470997 9.80665
0.3 0.4412992 2.451662 9.80645
0.4 0.7845320 3.432328 9.80666
0.5 1.225831 4.411299 9.80662

I did not ask for the speedometer and accelerometer graphs to be plotted
on the screen (or for the values of v and g displayed) but those services
are available. The effect of air resistance? No problem either. Just click
on one of the two air resiastance force formulas and enter k:

Fair= k*v*("projected area" of your object) k from 0 to 10 kg/(m*s)
Fair= k*v^2*("projected area" of your object) k from 0 to 10 kg/(m*m)

A more realistic algorithm for Fair can also be imposed. Do you want to
collect free fall data for another planet? Just enter a new value of g
and appropriate numbers will be produced for you. Analyse the data and
the imposed value of g will result. And you are no longer restricted to
distances which are much smaller that the radius of your chosen planet.
Choose the GRAVITY command from the WORLD menu and click the "planetary
gravity" button. The radial dependence of g will be taken under
consideration while the data are simulated.

No, I am not one the stockholders of IP. I just like this program very
much. And I plan to use it, occasionally. But not for verifying that in
the real reality the value of g is not changing.
Ludwik Kowalski