[meteorite-list] Velocity a meteorite hits the ground?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 9 Apr 2009 02:08:49 -0500
Message-ID: <6ED83D67C80D467895FE7B8B1B8133F4_at_ATARIENGINE2>

Hi,

The speed at which an object reaches the ground
depends on the distance it has fallen, balanced
by the retardation of air resistance. A smooth, pointed
projectile falling from 42,000 feet will achieve a terminal
velocity of about 900 mph, while an irregular floppy
object like a man without a parachute, screaming and
flailing his arms and legs, would be hard pressed to
exceed 135 mph.

In the case of a meteorite, it "falls" from the stagnation
point which is the altittude at which it almost "stops,"
then starts to free-fall. The faster the meteoroid comes
in, the lower the stagnation point (if stagnation occurs
at all) and the shorter the drop. Smallish meteorites
(< 10 kg) that are recovered after damaging things (the
famous "hammers") seem to have been moving at
approximately 250 mph +/- 100 mph.

Hailstones fall from the tops of clouds after having been
tossed up and down repeatedly until they accumulate
enough ice weight that the air currents cannot support
them any more. The nasty bruising ones are probably
in the 30 to 50 mph range. The heavy two-inch ones
are not any faster but are capable of doing real damage,
like breaking bones.

The role of air resistance is mathematically complex
but the principal factor is how much or little mass the
falling object possess for its resistive area. If someone
tosses a man down a 100-foot mine shaft to the rocky
floor, he is unlikely to survive. If someone tosses a cat
down the same 100-foot mine shaft, he might break
some small bones in the foot or lower leg or he might
not if he's a really fluffy cat. If someone tosses a mouse
down the 100-foot shaft, the mouse lands on his feet,
shakes his head dizzily, and says, "What the hell was
that all about?" although to our ears it sounds like
"Eeeek!"


Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "Aubrey Whymark" <tektites at googlemail.com>
To: <Meteorite-list at meteoritecentral.com>
Sent: Thursday, April 09, 2009 12:23 AM
Subject: [meteorite-list] Velocity a meteorite hits the ground?


> Hi
>
> I'm sure this is a very simple question. The other day I was caught in
> a hail storm and was hit by 30-35mm diameter hail stones. One hit my
> exposed hand and made a nasty bruise. At what speed were these hail
> stones falling? By comparison, at roughly what speed do meteorites
> fall assuming they have lost all of their cosmic velocity. I am
> assuming it will be a little faster as meteorites are heavier and so
> the drag will have less of an effect.
>
> Thanks, Aubrey
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Received on Thu 09 Apr 2009 03:08:49 AM PDT