A freight car weighing 2 . 5 2 . 5 x 1 0 ^4 1 0 4 kg runs into another freight car of the

 A freight car weighing $2\mathrm{.}5$ x $10\mathrm{^4}$ kg runs into another freight car of the same weight. The first

 

was moving at $34$ m$/$s north and the second was at rest. If the cars are coupled together after

 

the collision, what is their final velocity?