This is true chordates are vertebrae
A billiard ball moves with 3 kg⋅m/s of momentum and strikes three other billiard balls that have been just sitting there at rest and not moving.
The total momentum of all four balls after the collision is <em>3 kg⋅m/s</em>, because momentum is not created or destroyed. The total amount of it after an event is the same as the total amount of it before the event.
