Heres the problem Im working on

http://img91.imageshack.us/img91/1161/cartz0.jpg

Im trying to figure the setup to find which car was going faster and how fast....

Would I set up the equation before the collision and after...the collision is perfectly plastic so

$\displaystyle m_{a}v_{a} + m_{b}v_{b} = (m_{a} + m_{b})v\prime$

also since its perfectly plastic

$\displaystyle v\prime_{b} = v\prime_{a} = v\prime $