Re: Smart PASCO Pulley

[sample@lyon.edu (John D. Sample)]

At 8:29 PM on 3/28/97, <phys-l@mailer.uwf.edu> wrote:

> I was using the Smart PASCO Pulley today with Science Workshop Software.
> The smart pulley is in constant contact with a rotating disk so that
> as the disk spins the smart pulley spins.
>
> The angular acceleration should be negative at all times during a
> "spin down" of the disk (the angular velocity constantly decreases on
> the table and graph of data).  Instead there is an alternating pattern
> of negative and positive angular accelerations on both the table and
> the graph of the acceleration.
>
> Is anyone familar with this equipment and results?
>
> Writing this note makes me wonder if there is a data sampling rate that
> needs tweaking...but the question is posed for assistance! Thanks.
>
> Tim Burgess
Yes, I've seen this or something similar.  It was while using the older,
tan pulleys with 3 circular holes rather than the newer black pulleys with
10 slots.  This could be your problem if the alternating pattern in
acceleration is something like - - +, - - +.

We determined that we had pulleys with unevenly spaced holes.  The pattern
even changed from one pulley to the next.  This has also been observed by
one of the faculty at the Naval Academy (Dave Nordling).

The newer black pulleys are much better and give higher data rates; 10/rev
instead of 3/rev.  You can buy the pulleys without the photogates, and use
them with the old photogates.  I would hope the software you use would
allow you to specify the # of holes per rev.  Dave and I wrote our own
drivers for these pulleys using LabVIEW so we had complete control over how
the data was handled...I'm not familiar with the PASCO or other prepackaged
software.

Chip