A 1,600 kg train car rolling freely on level track at 16 m/s bumps into a 1.0 * 103 kg train car moving at 10.0 m/s in the same direction, and the two latch onto each other and continue together. What is their final speed?

A.) 16 m/s

B.) 6.0 m/s

C.) 10 m/s

D.) 14 m/s

This item is solved through the concept of the conservation of momentum which states that the momentum before and after collision should be equal.

momentum = mass x velocity

(1,600 kg) (16 m/s) + (1.0x10^3 kg) (10 m/s) = (1600 + 1000 kg) (x)

The value of x is 13.69 m/s. Thus, their final speed is approximately letter D. 14 m/s.