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Re: [Phys-L] fidget spinner: more data, more analysis, timestamps, force-law plot




On 2017/Sep/20, at 10:29, John Denker via Phys-l <phys-l@mail.phys-l.org> wrote:


For one thing, we notice that the speeds are an order of magnitude
smaller. It appears that the v^2 term (presumably aerodynamic
drag) is not noticeable here. There is a small linear term, plus
a constant term. The constant term goes away at the very smallest
speeds, as it must, since the net force must go to zero at zero
speed.

I do not have a microscopic physical explanation for the constant
term. It will require more thought than I can give it at the moment.

4) The new plot looks noisy.

The untrained human eye is not a good way to analyze noisy data.
It would be nice, from a user-interface point of view, to find
a way to smooth the data ... but that comes later! From a
fundamental physics point of view, the noisy data is the real
data. It carries more information than the smoothed data would,
and I am very happy to see it as-is.

The expert will spend a lot of time and effort looking at the
raw data before deciding how (and whether) to smooth it.
______________________________________________


I flipped it rather weakly, as I feared it would be too fast (time/revolution too short) for the MicroSet to collect W/O error. It’s the only data I took. I intend to take more tonite.

All data I’ve taken of pendula have been very noisy. I don’t think it’s artifacts. Remember the resolution is ~ a microsec. My analyzer (Kaleidagraph) has smoothing functions.

A much faster spin, I think, will result ina quad. term. And the MicroSet will average beat up to 256 beats.


bc later