Three objects travel. Object P (4 kg) travels downward at 8.3 m/s. Object Q (2 kg) travels to the east at 7.2 m/s. Another object (R) is traveling at them from the south east corner. What is the magnitude of the momentum of object R so that the combined masses remain stationary after they collide? I figured out that you simply create a triangle of the momentums, finding that 36 is the magnitude of the momentum of object R as the right answer. However, I don't really get what I did completely. Is it because this triangle represents conservation of momentum? Isn't the object R coming from the south east a seperate factor? As in, as the hypotenuse of the triangle, doesn't it represent final momentum....? Little confused here.