File:Collisioncartsm1greatergreaterthanm2.gif

English: When the first body is much more massive than the other (that is, m1 » m2), the final velocities are approximately given by

${\displaystyle \mathbf {v} _{1}=\mathbf {u} _{1}\,}$

${\displaystyle \mathbf {v} _{2}=2\mathbf {u} _{1}-\mathbf {u} _{2}\,.}$

Thus the more massive body does not change its velocity, and the less massive body travels at twice the velocity of the more massive body less its own original velocity. Assuming both masses were heading towards each other on impact, the less massive body is now therefore moving in the opposite direction at twice the speed of the more massive body plus its own original speed.

This example m1=1000kg, u1=5m/s, m2=0.1kg, u2=0m/s, the final velocities are approximately given v1=4.999m/s, v2=9.999m/s