Question

A hockey puck moving due east with speed 1.00 m/s collides with an identical puck moving 40 degrees south of west with speed 2.00 m/s. After they collide, the first puck is moving south with speed 1.50 m/s. What is the direction and speed of the second puck?

Answer 1

break up each puck into N, E components. Then use the law of conservation of momentum in each direction.

N:
0-M*2sin40=-M*1.5+M*Xn
notice the M's divide out. Solve for Xn, the north component of the second puck.
E:
M*1-2Mcos40=0+MXe
solve for Xe, the east component of the second puck.