התנגשות אלסטית

u_{1}=u'_{1}+v_{cm}=-v'_{1}+v_{cm}=-\left(v_{1}-v_{cm}\right)+v_{cm}=-v_{1}+2v_{cm}

u_{1}=-v_{1}+2\cdot\frac{m_{1}v_{1}+m_{2}v_{2}}{m_{1}+m_{2}}=v_{1}\cdot\frac{m_{1}-m_{2}}{m_{1}+m_{2}}+v_{2}\cdot\frac{2m_{2}}{m_{1}+m_{2}}

u_{2}=v_{2}\cdot\frac{m_{2}-m_{1}}{m_{1}+m_{2}}+v_{1}\cdot\frac{2m_{1}}{m_{1}+m_{2}}