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If for a system of N particles of different masses m1, m2, . . . mN with position vectors $${\overrightarrow {\bf{r}} _1},\,{\overrightarrow {\bf{r}} _2},\,.\,.\,.\,{\overrightarrow {\bf{r}} _N}$$    and corresponding velocities $${\overrightarrow {\bf{v}} _1},\,{\overrightarrow {\bf{v}} _2},\,.\,.\,.\,{\overrightarrow {\bf{v}} _N}$$    respectively such that $$\sum\limits_i {\overrightarrow {{{\bf{v}}_i}} = 0,} $$   then

If for a system of N particles of different masses m1, m2, . . . mN with position vectors $${\overrightarrow {\bf{r}} _1},\,{\overrightarrow {\bf{r}} _2},\,.\,.\,.\,{\overrightarrow {\bf{r}} _N}$$    and corresponding velocities $${\overrightarrow {\bf{v}} _1},\,{\overrightarrow {\bf{v}} _2},\,.\,.\,.\,{\overrightarrow {\bf{v}} _N}$$    respectively such that $$\sum\limits_i {\overrightarrow {{{\bf{v}}_i}} = 0,} $$   then Correct Answer the total force on the system must be zero

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