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Two cars each with mass $M$ are heading towards each other, one with velocity $v_1 = -2 m/s$ and the other with $v_2 = 3 m/s$.

What is the speed of the center of mass of the two-car system?

$\frac {1} {2} m/s$

$ 1 m/s$

$\frac {3} {2} m/s$

$\frac {5} {2} m/s$

$ 5 m/s$