On 5/10/09 12:10 PM, "Hal Murray" <hmur...@megapathdsl.net> wrote:
>
>
>> As a model for what they're trying to do, say you were going to
>> measure the acceleration due to gravity by videotaping a falling
>> object against a scale in the background. Except that the motion is
>> more complex.. Maybe imagine putting an accelerometer in the "payload"
>> of a trebuchet... And you want to time align the position of the
>> trebuchet components (from the video) with the forces on the payload.
>> That's not what they're doing, but now that I describe it, that WOULD
>> be a cool science project. And get away from the "here, I built a
>> trebuchet and launched a projectile X meters" which is kind of tired.
>> (get one of those analog devices 3 axis accelerometers, hook it to a
>> suitable datalogger..)
>
> For something like that, you could:
> start the camera
> start the recorder in the payload
> whack the payload with a stick to inject a calibration marker
> (the stick has to be visible in the camera)
> maybe re-aim the camera
> launch the payload...
>
>
>
Yes.. This is called a "slate" or "clapper board" in the movie trade.
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