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Re: Help!! etc.



I think you've hit on the explanation, Roger. Oddly enough, I had a
student ask about this just this morning and after pondering it a while I
checked the "averaging" setting. The standard settings for MacMotion
average groups of 7 points in order to perform the velocity and
acceleration calculations.

Bob Stair
Dakota Ridge High School
Littleton, Colorado
rstair@jeffco.k12.co.us

On Wed, 9 Oct 1996, Roger A. Pruitt wrote:

Also, remember that the distance probe (Sonic Ranger) measures distance as a
function of time. Values of velocity are computed from distance and time
measurements. Acceleration values are computed from computed velocity and
time values. The acceleration graph will be quite "noisy" as a result.
However, think about the first calculations of velocity and acceleration from
insufficient distance-time data. We know from calculus that the derivative of
a discontinuous function will be infinite at the point of discontinuity. At
the start of cart motion we have a discontinuity which will produce an
overshoot in the acceleration. I don't know the algorithm in the Vernier
software. It may not use adjacent data points, but rather alternate data
points in computing velocity and acceleration. Does anyone on the list know
the specifics?

Roger