Measuring Speed Decay - Calculating Time to Stop

AI Thread Summary
To measure the speed decay of a rolling ball, one can record the time it takes to travel fixed distances multiple times. With these time measurements, it's possible to calculate the initial speed and analyze the data to determine deceleration. Curve fitting techniques, such as polynomial fitting, can be employed to model the motion based on the collected data points. Additionally, using video or stroboscopic methods can provide visual data to enhance accuracy. The goal is to derive a formula that predicts how far the ball will travel based on initial measurements.
phutoo
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Hi, I was wondering how I would find the speed decay of a ball rolling in a straight line, if i were to measure the time it takes to travel a certain distance over and over. i.e
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[FONT="Courier New"]
>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>
<---10cm--> <---10cm--> <---10cm-->
           ^           ^           ^
      record time  record time  record time

So then with those 3 time measurements (or less), could the time be calculated for when the ball will stop? This is just a question I've been thinking about for a couple of days and I just can't figure it out :)
 
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You'd end up with 4 samples of position versus time to work with. You could then use this information to do a curve fit, perhaps a polynomial, or you could assume some specific equation type and do an exact fit.
 
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If the ball happens to be going fairly quickly, a TV movie could show you the separate images of the ball at successive 1/60th second intervals (or whatever frame rate you happen to be using.)
Failing that, a stroboscope with, say 1/10s flashes and a camera set to long exposure (dark room, of course) could also give you a set of sharp images on the same picture. Do the whole thing in front of a metre rule and all the info (times and distances) is there on the picture for you
 
Yes but the problem is I want to be able to calculate the distance it will travel just from a few measurements at the beginning.

I'm not too sure about what you said rcgldr; how would I fill in the rest of the curve?

I was thinking from the first time measurement, I would have time and distance, so I could calculate the speed at that point to be dist / time. But then how could I calculate the de-celeration? or am I going about this all wrong? :)
 
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