Question

An old go-kart with a mass of 300 kg is traveling in a straight line at 80 m/s. It is
followed by a 4-wheeler with mass of 200 kg moving at 60 m/s. How fast is the center
of mass moving?

Answer 1

$$v_{cm}=\frac{m_1v_1+m_2v_2}{m_1+m_2}\\ v_{cm}=\frac{300(80)+200(60)}{300+200}=72\frac{m}{s}$$