A particle of mass ${\mathrm{m}}_1$, collides head on with a stationary particle of mass ${\mathrm{m}}_2$. If $\frac{{\mathrm{m}}_1}{{\mathrm{m}}_2}>\mathrm{e}$, where e is the coefficient of restitution, then: 

${\mathrm{m}}_1\mathrm{v} = {\mathrm{m}}_1{\mathrm{v}}_1+{\mathrm{m}}_2{\mathrm{v}}_2$ and ${\mathrm{v}}_2-{\mathrm{v}}_1 = \mathrm{ev}$

on solving ${\mathrm{v}}_1 = \frac{\mathrm{v}({\mathrm{m}}_1-{\mathrm{em}}_2)}{({\mathrm{m}}_1+{\mathrm{m}}_2)}$

Given 

$\frac{{\mathrm{m}}_1}{{\mathrm{m}}_2}>\mathrm{e}$

$\Rightarrow {\mathrm{m}}_1-{\mathrm{em}}_2>0$

so, ${\mathrm{v}}_1$ is positive and thus ${\mathrm{m}}_1$ will move in same direction.