Final answer:
A person can indeed have the same momentum as a train if they are moving fast enough, due to the momentum being the product of mass and velocity. The total momentum of two colliding air cars of equal mass will be equal before and after the collision, according to the law of conservation of momentum. For coupled train cars, their final velocity after collision can be determined by conservation of momentum calculations.
Step-by-step explanation:
It is true that a person can have the same momentum as a train. Momentum is defined as the product of an object's mass and velocity (momentum = mass × velocity). Therefore, if a person was moving fast enough, they could have a momentum that is equivalent to that of a slower-moving train, despite the large difference in mass. For example, if a train has a large mass but is moving slowly, its momentum could be matched by a person with a much smaller mass moving at a high velocity.
In the case of the two air cars, A and B, of equal mass, where before the collision car A has a certain speed and car B is at rest, the total momentum of the two cars will be equal before and after the collision according to the law of conservation of momentum, assuming an isolated system and no external forces.
When applying the conservation of momentum to the example of the train cars being coupled together, the final velocity after the collision can be calculated by using the conservation of momentum formula, taking into account the mass and velocity of both train cars before the collision.