User talk:212.7.28.207

"We know that v ¯ C o M ⋅ ∑ i m i v ¯ i ′ = 0, {\displaystyle {\bar {v}}_{CoM}\cdot \sum _{i}m_{i}{\bar {v}}'_{i}=0,} {\displaystyle {\bar {v}}_{CoM}\cdot \sum _{i}m_{i}{\bar {v}}'_{i}=0,} so if we define:" I think this part could use some explanation