Additional data are reported that confirm a theory presented in a previous paper for the penetration of a stable flat‐nosed projectile in sand. The negative acceleration of the projectile can be expressed by the relations: -dv/dt=αv2, v0≫v≫vc; -dv/dt=βv2+γ, vc≫v≫0 where the coefficients α, β, γ are positive constants and v0 is the striking velocity. In the case where air is removed from the sand and the sand is loaded transverse to the trajectory by one atmosphere pressure, the coefficients α and β are characteristic of inelastic and elastic impact, respectively, where the flow process is regarded as Newtonian. An additional experiment has been performed where quartz powder produced by impact is plotted as a function of initial projectile energy. Although the powder production curve can be represented roughly as a straight line through the origin, there are small discontinuities in slope corresponding to the critical velocity v=vc. The velocity of sound in sand has been measured under the conditions of the experiments. Loading increases the velocity of sound markedly but has little effect on the critical velocity vc.
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