What is final speed

Question

A freight car with a mass of 3.5 x 105 kg traveling at 5 m/s connects itself to another identical freight car at rest. What is their final speed together after the collision

Answer 1

Arturo's remarks are appropos.

 

I think that the question ought to be worded as follows:

What is their COMBINED speed together IMMEDIATELY after the collision?

because I believe the final speed will be zero, if friction is allowed to operate, or will be zero at the end of their trip.