What must the total momentum of the system be after the train cars collide?

Answer:The total momentum of the system remains the same.Momentum before collision is equal to momentum after collisionStep-by-step explanation:Momentum is defined as the product of mass and velocity of the bodies.According to the law of conservation of momentum, a collision that occurs in an isolated system, the momentum before collision equals that after collision.After collision, the bodies can move in the same direction thus their momentum is combined.