LINEAR momentum velocity of second PARTICLE after collision WOULD be \[\frac{V}{3}\] Coefficient of restitution is \[e=\frac{relative\,\,velocity\,\,ofseparation}{relative\,\,velocity\,\,of\,approach}=\frac{V/3}{V}=\frac{1}{3}\]Loss in kinetic ENERGY \[=\frac{1}{2}v{{V}^{2}}-\frac{1}{2}(3m){{\LEFT( \frac{V}{3} \right)}^{2}}=\frac{1}{3}m{{V}^{2}}\]