Direct measurements (2): ballistics
For a vertical gas jet
v0 = (2 g hmax) 1/2
Example: Stromboli
hmax = 100 m
v0 = 50 m/s
v0 is not too sensitive to hmax, which is difficult to measure
Impact on the ground: xa
xa
=
v02 sin( 2a)
2 g
a=
60 °; v0 = 50 m/s; xa = 220 m
xa is maximum for a = 45 °
Maximum distance reached by
ballistics ejecta: a few km.
If a small plume is formed,
small ejecta can be carried further away
(kinetic energy is transformed into potential energy)