Howdy!
The bullet traveling at high velocity through the air, or any medium for
that matter, has a vacuum behind it. If it's traveling near or greater than
the speed of sound, it also develops a shock wave around it. The shock wave
makes the bullet effectively larger in diameter, and the vacuum behind it
makes the bullet effectively longer. At the speed of sound (~1100 ft/sec)
the bullet with surrounding shockwave and trailing vacuum goes from just
outside the can to just before exiting the can in about 200 microseconds
(0.0002 seconds). The bullet plus it's shockwave plus it's vacuum is now
displacing the fluid in the can nearly instaneously! The fluid, unlike air,
is incompressible and can't flow through the bullet hole rapidly enough in
such short period of time. The pressure therefore rises (in this same 200 or
so milliseconds) to what would be near infinite save for the can bursting.
This pressure in the can propagates to every part of the can at the rate of
about 4800 ft/sec (approx. velocity of sound in water), so the bursting
pressure of the can is approximately the same around the entire can. The
bursting will take place first at the weakest points of the can (usually at
the seems), bullet holes and the center of the longitudinal part of the can.
With enough energy, the can should turn nearly inside out.
The same thing happens when you shoot fruit, like apples or water melons as
they are mostly water. The whole thing bursts with extra burst flow at both
the entry and exit which can be seen using high speed photography - speed
usually provided by a fast strobe.
I shoot fruit all the time, as it's hyper velocity dart fun and the exploded
fruit is biodegradable, usually eaten as a feast by the various denizens of
the desert after I leave. A .270 rifle bullet at Mach 4 hitting a water
melon is quite impressive.
Regards,
Bob...
Engineer, firearms enthusiast.
-----------------------------------------------------------------
Note: No trees were killed in the sending of this message,
but a large number of electrons were terribly inconvenienced.
From: "ADavidhazy" <andpph@xxxxxxx>
Marilyn,
I am no physicist but I believe that once the bullet has entered the
can and it is pushing its way to the other side it displaces liquid
and this has to go somewhere and the only free space is the hole it
placed where it entered ... so backwards. Later on the second, exit,
hole appears and liquid is also able to go that way plus the bullet
drags some along as well probably.
In some way morbid this is related to the discussions about president
Kennedy's assassination.
Marilyn Dalrymple wrote:
Why is it the can blows out all the way around? I would think that the
side where the bullet goes in would sink in, the side where the bullet
leaves the can would go out. Is it due to the "explosion" of the
carbonated liquid in the can, or does the bullet itself cause this?
