Example 9.4 in the essential university physics: Jumbo, a 4.8-t elephant, is standing near one end of a 15-t railcar, which is at rest, all by itself, on a frictionless horizontal track. Jumbo walks 19m toward the other end of car. How far does the car move?
I have several questions about this example
If the system including jumbo and the car, then the centre of mass of this system is not moving since there is no external net force. So is the cm not moving relative to the ground?
Does the car move because the elephant exerts a friction to the car toward left?
If taking the car itself as the system, then does it has a external net force which is the friction? If it is, then will it run to the left forever? If it will, how can the centre of mass not moving?