Hi guys, I am new here and I am having a LOT of trouble with this new momentum stuff, which I failed in Here's a question: A billiard ball has mass 210 g. It's hit with spin and bounces off the side of a table. The initial speed of ball is 1.6 ms-1 (at angle of 60 degrees) and its final speed is 0.8ms-1 (at angle of 30 degrees) 1) Find the change in the momentum of ball due to collision I had trouble even starting the question. I drew the normal between the collision, and did 90-30=60 to find the inside angle and 90-60=30 for the other. Is anyone able to give me a hint on what formula to use? I'm not familiar with this because I usually do the problems with same initial and final speed.