A ball of clay of mass m1 = 10 kg and horizontal speed of V1 = +10 m/s collides head-on (that is they are traveling along the same line, but in opposite direction) with a ball of putty of mass m2 = 10 kg and a horizontal speed of V2 = −9. The two balls stick together. How fast and in which direction ("+" or "-") are they moving after the collision? Your Answer: Answer units