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Re: Air resistance



Using Ludwik's data, spread sheet, and simple 'eye-ball' fits I get equally
good results with:

n b
1 .05
2 .03
3 .017
4 .010
5 .0055

With the data I have for a falling foam ball over a distance from .3 to 12
meters I can also get equally good eye-ball fits with:

n b
1 .00475
2 .0011
3 .00025
4 .00005
5 .00001

For Ludwik's data, b must be changed by 75-100% between n's while with my
data almost 500% between each n. Also, the theoretical 'b' for a sphere
experiencing a v^2 air resistance force (.5*C*rho-air*area--where C = .5 for
a sphere) IS .00106 for the ball used in this experiment--in perfect
agreement with the best fit above.

Given enough adjustable parameters, one should be able to fit any curve with
any given value for one of the parameters. The drag coefficients do have a
physical basis (sorry I don't have formulae for other than the v^2
dependence), and unless the theoretical b's are also close to the best fit
values, then it seems like v^2 is certainly preferred with my data. I
don't know what the theoretical b is for Ludwik's geometry.

Rick


-----Original Message-----
From: LUDWIK KOWALSKI <KOWALSKIL@alpha.montclair.edu>


t(s) d(m) v(m/s) a(m/s^2) R(N)

1.050 0.714 1.506 4.34
1.075 0.757
1.100 0.800
1.125 0.845
1.150 0.883
1.175 0.927
1.200 0.987
1.225 1.045
1.250 1.103
1.275 1.165
1.300 1.229
1.325 1.306
1.350 1.364
1.375 1.430
1.400 1.500
1.425 1.591
1.450 1.677
1.475 1.744 3.117 1.73