Answer:
Velocity is a vector whose magnitude is called speed. Collision study needs to analyse the transfer of momentum, which is another vector quantity associated with the velocity vector of each object
Step-by-step explanation:
The important concept to recall is that velocity is a vector quantity, which has direction apart from just magnitude (as speed is). So in the transfer of momentum (another vector quantity) that takes place in a collision, it is extremely important to know the direction of the velocity vector, since there is much larger transfer of momentum if the cars collide heads on, than if the cars collide from behind while going in the same direction.