5.6 Main Ideas

Conservation of Momentum: the sum of the momentum in a system before a collision equals the sum of the momentum in the same system after a collision. In other words it is conserved in the x-direction and the y-direction 

$$\begin{gathered} \sum _{}{\overrightarrow{p}}_i=\sum _{}{\overrightarrow{p}}_f \\ \sum _{}{\overrightarrow{p}}_{ix}=\sum _{}{\overrightarrow{p}}_{fx} \\ \sum _{}{\overrightarrow{p}}_{iy}=\sum _{}{\overrightarrow{p}}_{fy} \end{gathered}$$