I am a little lost on where to begin with this problem. In my mind, it has something to do with a 90 degree angle, so it would require the use of sin or cos. But I may be wrong. Any help would be appreciated. It is due tonight. Problem: A 20 g ball of clay traveling east at 4.5 m/s collides and sticks together with a 60 g ball of clay traveling north at 8.5 m/s. What is the speed of the resulting ball of clay?