A 150kg cart moving at 13m/s east collided with a 420kg wagon

lcp1992

1. The problem statement, all variables and given/known data
A 150kg cart moving at 13m/s east collided with a 420kg wagon moving at 5m/s east.The cart rebounded westward with a speed of 3m/s. What was the speed of the wagon after the collision?


2. Relevant equations

m1v1+m2v2=m'1v'1+m'2v'2


3. The attempt at a solution
I solved the problem with this formula but i got 8.57m/s as the answer but the correct answer should be 11m/s.

Zula110100100

Watch your signs(+/-)

lcp1992

thanks!!