Function w(U_∞) in Equation (68), computed from ﹩\sqrt{2}-1﹩ to ﹩\sqrt{2}+1﹩. These boundaries are where an intersecting particle cannot be ejected and one where it would initially be hyperbolic, respectively. A maximum ﹩{w}_{{\rm{\max }}}={2}^{3/4}﹩ is reached at ﹩{U}_{\infty }=1/\sqrt{3}﹩. The function drops to zero at both boundaries.