A 1500 kg car traveling at 90 km/hr East collides with a 3000 kg truck traveling at 60 km/hr South. They stick together and move which direction?

They both move towards South direction.

Explanation:

NB: The car traveling due east must be backing west and the car traveling due south must be backing north.

From their momentum in calculation below:

Momentum of the car traveling east is MU = 1500x90x1000/3600 = 37,500kgm/s.

Momentum of car traveling due South = MU = 3000x60x1000/3600 = 50,000. So, from here we see the the momentum of the car moving south has the high momemtum so they stick together and move towards the direction of south.