Re: [Phys-L] impacts

[John Gastineau <jgastineau@vernier.com>]

Regarding Bernard's query on the temporal resolution of the force plate:

A force sensor can be modeled by a mass on a spring. From the compression
you know the force. But, that also means that the darn thing has a resonant
frequency. That limits the response time.

If you apply shorter and shorter impulses to any real force sensor,
eventually you see not the duration of the impulse, but the response time
of the sensor.

For the force plate, the response time is on the order of 20 ms--much too
long to look at a baseball impact time.

I love questions like this that get at the behavior of real, as opposed to
ideal, sensors. We often spend time talking about the difference between a
real and an ideal voltmeter and its impact on a circuit, but we don't often
talk about real force sensors.

John

--
John E Gastineau
Staff Scientist and Partner
Vernier Software & Technology


On Fri, Nov 25, 2016 at 9:32 PM, bernard cleyet <bernard@cleyet.org> wrote:

> I’m too lazy (code for I have other things to do) to experiment before
> suggesting, but …
>
>
> The Vernier force plate might give you an idea for a base ball against a
> plate w/ a high force constant.  I’m too long using the interface, so I
> can’t even guess the time resolution.  Exploration of Vernier’s site may
> reveal a report on this experiment.
>
>
> https://www.vernier.com/files/manuals/fp-bta.pdf
>
> bc has force plate, suspects time resolution insufficient, and lazy.
>
>
>
> On 2016/Nov/25, at 20:56, Anthony Lapinski <alapinski@pds.org> wrote:
>
> Thanks for the cool video links! I wanted something simpler -- just a table
> of impact times. I think I saw one in a physics book years ago.
>
> On Fri, Nov 25, 2016 at 11:43 PM, John Denker <jsd@av8n.com> wrote:
>
> On 11/25/2016 07:47 PM, Anthony Lapinski wrote:
>
> baseball on bat,
>
>
> If I were doing it, I might contact the photographer of
> one of the videos and beseech him for a clean copy.
>  https://www.uml.edu/Engineering/Mechanical/Staff/Drane-Patrick.aspx
>  https://scholar.google.com/scholar?hl=en&q=%22patrick+drane%22
> and/or
>  http://www.soraphotography.net/
>
> If those guys don't have what you want, they ought to be
> able to point you to somebody who does.