<u>
The law of conservation of linear momentum
</u>
The sum of linear momentum of a system under no external force remains constant.
In this scenario although different forces act on two vehicles by each other when we consider the total system of two cars no external unbalance force act on them. So we can apply this law.
As law says,
The sum of linear momentum before collision = The sum of linear momentum after collision.
Sound waves are known to be the one that's not considered as a type of electromagnetic energy. As for microwaves and x-rays, they tend to share the same frequencies that can be considered as electromagnetic, and sound waves have a different frequency than them.
