I am having quite a bit of trouble with this problem. I would greatly appreciate any and all help and advice. Here's the problem: A fire cracker is thrown with velocity 12.0 m/s [W]. While moving in this direction, it explodes into two pieces. One piece has a mass of 2.1 g and moves with velocity 10.0 m/s [W 70 S] What is the velocity of the other piece which has a mass of 1.1 g? Ok. So far I understand that the fire cracker's momentum is Pfc=12m/s(3.3 g)= 39.6 gm/s The first pieces momentum is P1= 2.1 g(10m/s)= 21 gm/s i am having trouble deciding how to approach finding the velocity of the other peice. Do i use P total (before)= P total (after)??? And once I find the velocity how do i figure out which direction the piece is moving??? Thanks for any help you smart people can provide.