At 1:02 AM -0800 1/19/00, John A. Lind" <jlind@xxxxxxxxxxx> wrote:
Gary Edwards wrote:
>formerly airworthy Marine Corps Phantom. The engineering estimate of terminal
>velocity was between 80 and 99 mph. The OM-4 would be similar, taking 3.7 s
>or so to accelerate from zero to 80, requiring a cliff about 216 feet tall.
>How tall did this guy say he was?
>From the much longer message I sent off-list to the originator of this
thread (and posted here July '99 under "why you don't want to drop your OM"):
Assuming a table or waist level drop of about 1 meter
to the "hard" floor (concrete or hard tile over concrete?):
Terminal speed, 1 meter (~3+ foot) drop: ~16 kph or ~10 MPH
Time to impact: ~0.45 seconds
g forces at *point* of impact: 500 g's
(assumes uniform deceleration to 0 in .001 sec over .25mm or .01 inch distance)
The g forces on the point that strikes a "hard" floor are in the ballpark
of 300-500 g's based on our drop testing of packaging at work. Now imagine
suddenly becoming a couple hundred times your weight in a millisecond, or
even 10 milliseconds. ("Oh, the humanity!")
==============================
It's only very rarely, however, that the whole camera will land perfectly
aligned so as to decelerate like that. Usually you get crumpling of a
small region to a depth of 1mm or more, or you get a tumbling action that
spreads the deceleration over a centimeter or so. Given that even such
delicate creatures as hard disk drisk are often rated for shock loads of
200G...
For this particular case it's the "prism cracked in two" line that makes
me particularly suspicious -- I've seen some large solid hunks of glass
broken under impact, and that's an unlikely mode.
paul
Paul Wallich pw@xxxxxxxxx
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