Final answer:
The combined momentum of two colliding cars, one moving north and the other south, is an addition of both momenta considering their opposite directions, which yields a combined momentum of 2000 kgm/s to the north. The correct option is d).
Step-by-step explanation:
The question revolves around the concept of momentum, which is defined in physics as the product of an object's mass and its velocity. In this scenario, two cars collide, and we need to calculate their combined momentum. The momentum of each car is calculated individually and then combined, taking into account their directions since momentum is a vector quantity.
The first car with a mass of 900 kg and a velocity of 10 m/s to the north has a momentum of 900 kg * 10 m/s = 9000 kgm/s north. The second car with a mass of 1000 kg and a velocity of 7 m/s to the south has a momentum of 1000 kg * 7 m/s = 7000 kgm/s south.
To find the combined momentum, we subtract the momentum of the southern-moving car from the northern-moving car because they are moving in opposite directions, resulting in a combined momentum of 9000 kgm/s - 7000 kgm/s = 2000 kgm/s north.