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'[OT] Bang!'
2007\04\10@100106 by

Actually, this is EE, but I can't explain why.

Does anyone know where to find the acceleration of a baseball when it is hit?
I'm looking for high end numbers like in a major league home run.
Gee and Jerk if I can get it.

--
Jealousy is a disease, love is a healthy condition. The immature mind
often confuses one for the other, or assumes the greater the love, the
greater the jealousy. In fact they are almost incompatible; both at
once produce unbearable turmoil.
Jubal Harshaw, "Stranger in a Strange Land"
On 4/10/07, David VanHorn <dvanhornmicrobrix.com> wrote:
> Actually, this is EE, but I can't explain why.
>
> Does anyone know where to find the acceleration of a baseball when it is hit?
> I'm looking for high end numbers like in a major league home run.
> Gee and Jerk if I can get it.

Order of magnitude calculation:

Incoming baseball velocity:  -90mph  (good fastball) (note negative sign)
Homerun distance:  350 feet

Vy(t) = V sin(theta) - gt
Vx(t) = V cos(theta)

At end of flight Vy(t) = -Vy(0)

V sin(theta) - gt = -V sin(theta)

2 * V sin(theta) = gt

t = 2 * V sin(theta) / g

x distance:

x(t) = Vx(t) * t = V cos(theta) * 2 * V sin(theta) / g

Assume no air resitance, optimum angle on trajectory (45 degrees)

x(t) = 350 = 2 (V^2) sin(theta) cos(theta) / g

V = sqrt(g * d / (2 * cos(theta) * sin(theta)))

V ~= 106 ft/second

Assume impact takes place for a duration of 1/10th of a second:

a = (V1 - V0) / t

a = 106 - (-90) / 0.10

a = 1960ft/second^2

a ~= 61.25 g

Note that this is an AVERAGE acceleration, the real acceleration
will not be uniform over time, and there will be an instantaneous
acceleration much larger than this average.

Bill

--
Psst...  Hey, you... Buddy...  Want a kitten?  straycatblues.petfinder.org
Grrr... stupid mistake.  See correction below:

On 4/10/07, William Couture <bcouturegmail.com> wrote:
{Quote hidden}

And, if I wasn't in a hurry:

90mph = 90 * 5280 / 3600 = 132 feet/second

a = 106 - (-132) / 0.10

a = 2380ft/second^2

a ~= 74.38 g

Bill

--
Psst...  Hey, you... Buddy...  Want a kitten?  straycatblues.petfinder.org
>
>   a ~= 74.38 g

Ok, thanks, but that impact is what I'm looking to quantify.
I have times of 1/1000 to 1/2000 sec for the impact, various sources,
fair reliability I think.
On 4/10/07, David VanHorn <dvanhornmicrobrix.com> wrote:
> >
> >   a ~= 74.38 g
>
> Ok, thanks, but that impact is what I'm looking to quantify.
> I have times of 1/1000 to 1/2000 sec for the impact, various sources,
> fair reliability I think.

That seems rather fast, but OK...

Also, if you google "baseball impact physics", you quickly find
http://webusers.npl.uiuc.edu/~a-nathan/pob/

with a link to an article in the Nov. 2000 American Journal of
Physics:  "Dynamics of the baseball--bat collision"
http://webusers.npl.uiuc.edu/~a-nathan/pob/AJP-Nov2000.pdf

Bill

--
Psst...  Hey, you... Buddy...  Want a kitten?  straycatblues.petfinder.org
At 10:48 AM 4/10/2007, you wrote:
>>
>>   a ~= 74.38 g
>
>Ok, thanks, but that impact is what I'm looking to quantify.
>I have times of 1/1000 to 1/2000 sec for the impact, various sources,
>fair reliability I think.

"Physics of Baseball"

<http://webusers.npl.uiuc.edu/~a-nathan/pob/>

<http://www.iit.edu/~johnsonp/smart00/lesson3.htm>

<http://www.kettering.edu/~drussell/bats.html>

-- Alan

> That seems rather fast, but OK...
>
> Also, if you google "baseball impact physics", you quickly find
>   http://webusers.npl.uiuc.edu/~a-nathan/pob/
>
> with a link to an article in the Nov. 2000 American Journal of
> Physics:  "Dynamics of the baseball--bat collision"
>   http://webusers.npl.uiuc.edu/~a-nathan/pob/AJP-Nov2000.pdf

I had found some of the papers referenced, but not that page.

In the end though, too much information. I need something I can give
to a crystal vendor to say "has to withstand this".  The baseball vs
bat thing is an approximation anyway, so it's closer to an "order of
magnitude" answer that I'm looking for.
On Tue, 10 Apr 2007 11:40:48 -0400, you wrote:

>> That seems rather fast, but OK...
>>
>> Also, if you google "baseball impact physics", you quickly find
>>   http://webusers.npl.uiuc.edu/~a-nathan/pob/
>>
>> with a link to an article in the Nov. 2000 American Journal of
>> Physics:  "Dynamics of the baseball--bat collision"
>>   http://webusers.npl.uiuc.edu/~a-nathan/pob/AJP-Nov2000.pdf
>
>
>I had found some of the papers referenced, but not that page.
>
>In the end though, too much information. I need something I can give
>to a crystal vendor to say "has to withstand this".  The baseball vs
>bat thing is an approximation anyway, so it's closer to an "order of
>magnitude" answer that I'm looking for.

If the shock is very high, it may be worth looking at some of the various silicon based crystal
replacement devices that have appeared recently.
And of course consider if you actually need a crystal...

>In the end though, too much information. I need something I can
>give to a crystal vendor to say "has to withstand this".  The
>baseball vs bat thing is an approximation anyway, so it's closer
>to an "order of magnitude" answer that I'm looking for.

Seems if you really really need a crystal, then you are going to be
launching into MIL-SPEC territory if you are going to talk in terms of those
sorts of G forces. I am thinking in terms of electronics contained in shells
fired from cannons, but even then I don't think you are going to be looking
at the 90G I saw go by ...

Maybe you will end up with a resonator? Or is there some way you can use a
PIC on its internal oscillator? Seems to me that whatever you are doing is
going to have a short data collection time, so syncing things up at power on

>
> If the shock is very high, it may be worth looking at some of the various silicon based crystal
> replacement devices that have appeared recently.
> And of course consider if you actually need a crystal...

If this is what you mean:
http://www.chipdesignmag.com/display.php?articleId=140&issueId=  Then
yes, I still need a crystal.
> Maybe you will end up with a resonator? Or is there some way you can use a
> PIC on its internal oscillator?

Resonators are a poor second due to accuracy. Internal RC isn't workable.

> Seems to me that whatever you are doing is
> going to have a short data collection time, so syncing things up at power on

Don't try to pull too much from the "details" I've given. :)
On 4/10/07, David VanHorn <dvanhornmicrobrix.com> wrote:
>
> I had found some of the papers referenced, but not that page.
>
> In the end though, too much information. I need something I can give
> to a crystal vendor to say "has to withstand this".  The baseball vs
> bat thing is an approximation anyway, so it's closer to an "order of
> magnitude" answer that I'm looking for.

I wonder what the FoxTrax used?

http://en.wikipedia.org/wiki/FoxTrax
http://csdl2.computer.org/comp/mags/cg/1997/02/g2006.pdf

Not sure if it had a microcontroller on board, but it had IR emitters,
so I assume there was some kind of modulation used.

PS. Go Canucks! :-D
William Couture wrote:

> On 4/10/07, David VanHorn <dvanhornmicrobrix.com> wrote:
>> Does anyone know where to find the acceleration of a baseball when it is
>> hit? I'm looking for high end numbers like in a major league home run.
>> Gee and Jerk if I can get it.
>
> Order of magnitude calculation:
>
>    Incoming baseball velocity:  -90mph  (good fastball) (note negative sign)
>    Homerun distance:  350 feet

[...]

>    V ~= 106 ft/second
>
>    Assume impact takes place for a duration of 1/10th of a second:
>
>    a = (V1 - V0) / t
>
>    a = 106 - (-90) / 0.10

Why is it so difficult to convince people that SI units make sense? It's so
sad to see a good thought go down the drain because of silly unit errors :)

Using proper units with numbers in equations would help, too -- but when
not using SI units, this gets inconvenient rather quickly, so it's not that
common.

The last equation above would look like this, with the proper units:

a = (106 ft/s - (-90 miles/hr)) / (0.10 s)

Adding/subtracting ft/s to/from mph without conversion is not a good
thing...

The SI alternative would look like this:

a = (32.3 m/s - (-40.2 m/s)) / (0.1 s)

To me, this just looks like fewer conversion errors... :)

>    a = 1960ft/second^2
>
>    a ~= 61.25 g

The result would then be

a = 725 m/s^2 = 74 g

The number is not that different in the end (and in the same order of
magnitude), but that's just by chance. The factor from mph to ft/s is ~1.5,
but it could have been 3.8 just as well -- or instead of adding the
absolute speed values, they could have been subtracted and the result would
have been way off :-/

Gerhard

On 4/10/07, Gerhard Fiedler <listsconnectionbrazil.com> wrote:

> Why is it so difficult to convince people that SI units make sense? It's so
> sad to see a good thought go down the drain because of silly unit errors :)

Because I knew the values (90mph, 350feet) in American units, but not
SI units.  The conversion would have to be done anyway, and I made it
explicit.

And corrected myself about 10 seconds after I hit "send".  Which
actually puts me ahead of NASA.  :)

And, for a more detailed explanation of the dynamics and sample
calculations:
http://www.ch4549.org/baseball/hit4.htm