Date: Thu, 10 Jul 2003 12:13:38 -0700

Author: Eric Ayars

Subject: Re: Jerk

Post:

The one I used was a home-built circuit built around the ADXL105
chip, and I just threw it. If the Vernier model can be zeroed at
rest, that would take care of my problem. How do you keep the
measurement axis vertical?

> Sorry, I wasn't thinking about the pedagogy, I just wanted to
>see what would happen to an accelerometer in flight. I'm using the
>Vernier Low-g accelerometer with LoggerPro software. As Eric wrote,
>it is probably a stressed beam type of accelerometer, so it reads
>-9.8 while stationary because gravity is deforming the beam. But it
>can also be zeroed in that position so that it reads 9.8 in flight.
>Would that solve your problem Eric? By the way, how do you launch
>it?

--

-----------------------------------------------------------------
Dr. Eric Ayars
Assistant Professor of Physics
California State University, Chico
ayars@mailaps.org
From mkossover@mail.hockaday.org Thu Jul 10 15:45:13 2003
Message-id:
Date: Thu, 10 Jul 2003 14:45:27 -0500
Subject: Re: Jerk
To: tap-l@listproc.appstate.edu
From: "Marc Kossover"
References:
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Gary writes:
>They are a tricky device because they are not measuring force but
>acceleration. How would you take a force probe and an accelerometer and
>determine the mass of the object being pulled?


As far as I know, all accelerometers actually measure forces. Typically,
they have a known mass connected to a strain gauge. They generally can be
zeroed. The advantage over a force probe is that the components are all
internal and sealed into a small black box, making the device relatively
sturdy.

They usual come in different levels of precision -- less than 10g and more
than 10g. I guess the reference mass and the stiffness of the strain arm
are smaller in the low g case.

The most annoying feature of them is the cord, which sometimes gets in the
way and rotates the device, changing the axis of measurement. Hey, Dave
Vernier or folks at Pasco, any chance for a wireless model? How about a
wireless transmitter for all the probes?

Vernier sells a three-axis accelerometer that is pretty handy. Essentially
it is just three accelerometers put together in one package. It works
well, but is essentially three times the cost of the single axis probe.
This is handy for a variety of experiments including rotating platforms,
but I bring it up to solve the off axis problem from above. Have the
computer find the 3D composite acceleration and then look only at the
magnitude. Small rotations will become less important.

---

Although I have been known to put an accelerometer and a force probe
together for some labs, I try not to do that anymore, since it really is
cheating. Nowadays, I use the smart pulley (what a fine invention) with
the force probes.

Marc "Zeke" Kossover
The Hockaday School

From nicolenotz@yahoo.com Thu Jul 10 16:47:09 2003
Message-ID: <20030710204730.19495.qmail@web40803.mail.yahoo.com>
Date: Thu, 10 Jul 2003 13:47:30 -0700 (PDT)
From: Nicole Notz
Subject: Re: physics web sites
To: tap-l@listproc.appstate.edu
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www.PhysicsCentral.com
Has a "how things work" section and pictures , news,
research,
--- Winnmmw@aol.com wrote:
> Dear group,
> I am doing a workshop next week for new physics
> teachers in Hillsborough
> County. I will have about six or seven people. One
> of the things I would like to
> give them is a list of useful physics web sites.
> Anyone who has a suggestion
> for a site that would be helpful for new teachers,
> please let me know & I will
> compile a list.
> Thanks
>
>
> Mary Winn
>
> 2623 Watrous Ave.
> Tampa, FL 33629
> 813-254-3852
> winnmmw@aol.com
>


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From dimarco@physics.montana.edu Thu Jul 10 16:50:23 2003

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