Final Velocity Calculation for Inelastic Collision of Freight Trains

[rrosa522]

Homework Statement

Two freight trains have a completely inelastic collision at a track crossing. Engine 1 has a mass of 1.4x10^4 kg and is initially traveling at 45 km/h [N].
Engine 2 has a mass of 1.5x10^4 kg and is initially traveling at 53 km/h [W]. Calculate the final velocity.

Homework Equations

The Attempt at a Solution

p^2=p1^2+ p2^2
=(1.4x10^4)(12.5m/s)^2+ (1.5x10^4)(14.72m/s)^2
=281740m/s

The answer in the textbook is 9.7m/s. What am I doing wrong?

 

[rrosa522]

I just realized my mistake, i forgot to divide it by both mass