Answer:
Explanation:
Since momentum is a vector, you, indeed, in <em>two dimension</em> collisions, you can decompose it in two components, the x-direction and the y-direction, such as you do with the force, which is a vector too.
The law of conservation of <em>momentum</em> states that the total momentum before and after the collision are conserved.
Let's assume a collision in one dimension: x-direction.
If object A is moving to the right, its momentum is to the right. If objcet B is at rest its momentum is zero. Then, if when object A collides with object B, the first stops, the second must move to the right with a momentum in the x-direction equal to the momentum that object A initially had.
You can apply the same reasoning if object A is moving in two dimensions, and, a similar one, if object B is not at rest: at the end the momentum in each direction before the collision has to be equal to the momentum in each direction after the collision.