[meteorite-list] A "Strike" with a spare ball

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From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:45 2004
Message-ID: <46.484f290a.2d76affd_at_aol.com>

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Hola Rob,

You're right about the terminal velocity of a chondrite, in the shape of a
bowling ball being much faster than a conventional bowling ball. This might
still be a little counter intuitive, but, here are some 9 inch diameter bowling
ball terminal velocities (there's a lot of algebra behind all the numbers that
follow):

Doug's really heavy 14 pounder (6.35 kg): 153 mph (69 m/s)
Rob's super duper heavy 16 pounder (7.26 kg): 164 mph (73 m/s)
A bowling ball with a density of 2g/mL = 12.51 kg = 27.6 pounds: 215 mph (96
m/s)
Typical chondrite ball _at_ 3.65 g/mL (50.3 pounds or 22.83 kg): 291 mph (130
m/s)
Iron meteorite ball _at_ 8.0 g/mL (110.3 pounds or 50.0 kg): 431 mph (192 m/s)

Shield shaped Iron (Cabin Creek AR): 300 mph (134 m/s)
Oriented fat beer can shaped Iron at 50 kg (length = 3 times diameter): 700
mph (312 m/s)

Cabin Creek shaped Chrondrite: 202 mph (90 m/s)
Oriented fat beer can chrondrite as above: 473 mph (211 m/s)

So for a bowling ball shape, it would actually take an iron to achieve the
140 m/s, an ordinary chondrite falls somewhat slower, in the shape of a bowling
ball.

Could an ordinary Doug's bowling ball fall at the rate of a chondrite?
Maybe, at the limits. We have focused more on mass for the given cross sectional
area. But to fall at the same terminal rate, all that is required is the same
ratio of sqrt(mass)/sqrt(X-area) or really just mass divided by area being the
same. So, if it is twice the density, it needs to be cut in half. Could an
Iron fall at the same rate of the ordinary bowling ball? Probably not, but
for illustration, let's consider Cabin Creek, which is quite close to the 50 kg
- the same size as our bowling ball - and a wonderful oriented shield shape
I'd say around the dimension ratio 33 X 33 X 10. That actually gives around
double the surface area as the spherical solid bowling ball shape, so it probably
fell at about "only" 300 mph (134 m/s), close to a bowling ball chondrite.
In the other hand a cylindrical shape (I arbitrarily set the length three times
the diameter.

Of course there are other considerations like the frictional ablation
shaping, which is why cylinders turn into nosecones and bullets, and it is no wonder
that the Cabin Creek sample was know to be hot upon fall. All the
acceleration due to gravity holding back a 50 kg mass of iron several hundred miles per
hour is dissapated into heat. Alternately nosecones are more likely to be cool
and also with less thumbprinting.

The table above summarizes all my calculations, maybe there is an error, but
I hope not. This should clear up free fall of stones that lose their "cosmic
velocity" as well as for bowling balls, and how it fits in. A person
typically free falls at 110 mph or so thought they can double that by playing with
orientation. Ha. The calculations also showe this doubling effect for likely
masses. Keep in mind non iron meteorites are practically never going to stand
the shear frictional forces of shield shapes and "explode" into pieces. Also
for fun, an oriented bowling ball that fractures in exactly two hemispherical
pieces traveling terminally at 150 mph will leave the two fragments at a
terminal rate of ... 106 mph a piece. That's probably why "explosions" seem to
brighten fireballs. Suddenly the greater surface area for the same total mass
steps up the overal frictional energy released and the meteors slow down from an
instantly greater potential.

I get into this stuff. That's why I liked the bowling ball expt. which
really sounds like an excuse for some fun.

Saludos
Doug Dawn
Mexico

En un mensaje con fecha 03/02/2004 7:26:12 PM Mexico Standard Time,
ROBERT.D.MATSON_at_saic.com escribe:
>
> Hi Doug,
>
> Good point on the density of a bowling ball. Intuitively, I would have
> guessed
> the density was around 2 g/cm^3, when in fact it is barely above 1 g/cm^3
> --
> about 1.15 for a 16-lb ball (the mass I was assuming). An ordinary
> chondrite
> of the same size would weigh close to 50 lbs! So yes, air friction is
> going to
> be a serious factor, and a bowling ball isn't going to have a chance of
> reaching
> the terminal velocity of a chondrite (let alone that of an iron).
>
> To do this experiment properly, then, they're going to need to drop an
> object
> of the proper density. --Rob
>

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<HTML><HTML>Hola Rob, 
 
You're right about the terminal velocity of a chondrite, in the shape of a b=
owling ball being much faster than a conventional bowling ball.  This m=
ight still be a little counter intuitive, but, here are some 9 inch diameter=
bowling ball terminal velocities (there's a lot of algebra behind all the n=
umbers that follow): 
 
Doug's really heavy 14 pounder (6.35 kg): 153 mph (69 m/s) 
Rob's super duper heavy 16 pounder (7.26 kg): 164 mph (73 m/s) 
A bowling ball with a density of 2g/mL =3D 12.51 kg =3D 27.6 pounds: 215 mph=
(96 m/s) 
Typical chondrite ball  _at_ 3.65 g/mL (50.3 pounds or 22.83 kg): 291 mph=20=
(130 m/s) 
Iron meteorite ball _at_ 8.0 g/mL (110.3 pounds or 50.0 kg):  431 mph (192=
m/s) 
 
Shield shaped Iron (Cabin Creek AR): 300 mph (134 m/s) 
Oriented fat beer can shaped Iron at 50 kg (length =3D 3 times diameter): 70=
0 mph (312 m/s) 
 
Cabin Creek shaped Chrondrite: 202 mph (90 m/s) 
Oriented fat beer can chrondrite as above: 473 mph (211 m/s) 
 
So for a bowling ball shape, it would actually take an iron to achieve the 1=
40 m/s, an ordinary chondrite falls somewhat slower, in the shape of a bowli=
ng ball. 
 
Could an ordinary Doug's bowling ball fall at the rate of a chondrite? =
Maybe, at the limits.  We have focused more on mass for the given cros=
s sectional area.  But to fall at the same terminal rate, all that is r=
equired is the same ratio of sqrt(mass)/sqrt(X-area) or really just mass div=
ided by area being the same.  So, if it is twice the density, it needs=20=
to be cut in half.  Could an Iron fall at the same rate of the ordinary=
bowling ball?  Probably not, but for illustration, let's consider Cabi=
n Creek, which is quite close to the 50 kg - the same size as our bowling ba=
ll - and a wonderful oriented shield shape I'd say around the dimension rati=
o 33 X 33 X 10.  That actually gives around double the surface area as=20=
the spherical solid bowling ball shape, so it probably fell at about "only"=20=
300 mph (134 m/s), close to a bowling ball chondrite.  In the other han=
d a cylindrical shape (I arbitrarily set the length three times the diameter=
. 
 
Of course there are other considerations like the frictional ablation shapin=
g, which is why cylinders turn into nosecones and bullets, and it is no wond=
er that the Cabin Creek sample was know to be hot upon fall.  All the a=
cceleration due to gravity holding back a 50 kg mass of iron several hundred=
miles per hour is dissapated into heat.  Alternately nosecones are mor=
e likely to be cool and also with less thumbprinting. 
 
The table above summarizes all my calculations, maybe there is an error, but=
I hope not.  This should clear up free fall of stones that lose their=20=
"cosmic velocity" as well as for bowling balls, and how it fits in.  A=20=
person typically free falls at 110 mph or so thought they can double that by=
playing with orientation.  Ha.  The calculations also showe this=20=
doubling effect for likely masses.  Keep in mind non iron meteorites ar=
e practically never going to stand the shear frictional forces of shield sha=
pes and "explode" into pieces.  Also for fun, an oriented bowling ball=20=
that fractures in exactly two hemispherical pieces traveling terminally at 1=
50 mph will leave the two fragments at a terminal rate of ... 106 mph a piec=
e.  That's probably why "explosions" seem to brighten fireballs. =20=
Suddenly the greater surface area for the same total mass steps up the overa=
l frictional energy released and the meteors slow down from an instantly gre=
ater potential. 
 
I get into this stuff.  That's why I liked the bowling ball expt. which=
really sounds like an excuse for some fun. 
 
Saludos 
Doug Dawn 
Mexico   
 
 
 
En un mensaje con fecha 03/02/2004 7:26:12 PM Mexico Standard Time, ROBERT.D=
.MATSON_at_saic.com escribe: 
<BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT=
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"> 
Hi Doug, 
  
Good point on the density of a bowling ball.  Intuitively, I would hav=
e guessed 
the density was around 2 g/cm^3, when in fact it is barely above 1 g/cm^3=20=
-- 
about 1.15 for a 16-lb ball (the mass I was assuming).  An ordinary c=
hondrite 
of the same size would weigh close to 50 lbs!  So yes, air friction i=
s going to 
be a serious factor, and a bowling ball isn't going to have a chance of re=
aching 
the terminal velocity of a chondrite (let alone that of an iron).<F=
ONT COLOR=3D"#000000" BACK=3D"#ffffff" style=3D"BACKGROUND-COLOR: #ffffff"=20=
SIZE=3D3 PTSIZE=3D12 FAMILY=3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0"> 
  
To do this experiment properly, then, they're going to need to drop an obje=
ct 
of the proper density.  --Rob 
</BLOCKQUOTE> 
 
</HTML>
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Received on Tue 02 Mar 2004 10:50:21 PM PST

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