Answer
The speed of the two-sphere center of mass is $~~1.00~m/s$
Work Step by Step
Let $m_1 = 300~g$ and let the velocity $v_{1i} = 2.00~m/s$
Then: $~~v_{2i} = -2.00~m/s$
In part (a), we found that $m_2 = 100~g$
We can find the speed of the two-sphere center of mass:
$v_{com} = \frac{(300~g)(2.00~m/s)+(100~g)(-2.00~m/s)}{300~g+100~g}$
$v_{com} = 1.00~m/s$
The speed of the two-sphere center of mass is $~~1.00~m/s$
