Folks,
Here's a problem for you. I was interested in the risk due to the
falling pellets from a shotgun discharged toward the zenith. I assumed that
they would come down with nearly terminal velocity, so Stokes' Law should
give a reasonable estimate of their speed. For lead pellets with a diameter
of 1 mm, I calculated (to my surprise) that the terminal velocity would be
337 m/sec. There is a web site
<http://www.imagina.com/webpages/bbroadside/Big_Table_Metr.html> which
gives the muzzle velocity of various ammunition, which says that the exit
velocity from a 12-gauge shotgun is around 345 m/sec. Hmm? In the
calculation I used the viscosity of air at 18 degrees C (1.827 x 10^(-5)
N-sec/m^2), and did the calculation in both mks and cgs to make sure I had
not messed up the units.
Somehow, my sense is that falling pellets should not be very
dangerous if they hit you on exposed skin. However, if this calculation is
anywhere near correct, falling shotgun pellets would be very dangerous
indeed. What's wrong here?