math
posted by jr on .
A 1000·kg car traveling with a velocity of 13·m/s north collides headon with a 2000·kg truck traveling with a velocity of 17·m/s south. Immediately after the collision, the velocity of the car is 11·m/s south. Taking north as the positive direction, what is the velocity of the truck immediately after the collision?

conservation of momentum:
momentum before= momentum after
N means North, S means South, and N=S
1000*13N+2000*17S=1000*11S+2000*V
13000N+34000(N)=11000(N)+2000V
do a little algebra, and solve for V
In my head, I get
V= (1100021000)N/2000= 10m/s S
check that 
Thank you sooo much!!! I wasn't dividing by the right number!
can you also explain how to find the impulse of this problem?
A large truck with a mass of 6500·kg and going 20·m/s east collides with a car whose mass is 1100·kg and which is at rest. If the impulse exerted on the car by the truck is 12000·N·s east, find the impulse exerted by the car on the truck. Take east as the postive direction