Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

velocity averaging in MacMotion



A while back there was a discussion about strange acceleration
graphs obtained using Vernier Software's (Mac)Motion and the sonic
ranger. I indirectly asked the programmer, Stephen Beardsly, about
how the application finds velocity and acclerations from the
distance information.

After you set the number of points to use in the averaging dialog,
Motion does a quick least-squares fit to find the slope of that set
of 3, 5, 7, or whatever points and uses that slope for the velocity
at that time. Acceleration is determined similarly. Your students
will discover that the calculation is not a simple-minded successive
difference calculation such as might be done in a spreadsheet, as
mine did when I once had them check out a result from Motion.

Now, in Motion you can only change this setting before taking data, so
it's kind of hard to tell just how important the number of points
used is to the appearance of your graphs. I'm campaigning for this
after-the-fact averaging to be used in future versions of Motion for
Mac and Windows. We'll see.

JEG
-=================
John E. Gastineau
304 296 1966
Morgantown, WV
http://www.badgerden.com/~gastineau
email: gastineau@badgerden.com <==== NEW as of 10/1/96