A 4.0-kg meatball is moving to the right with a speed of 6.0 m/s directly toward a 2.0 kg meatball which is at rest. The two meatballs collide and stick together. What is their velocity immediately after
the collision?

Explanation:

The equation for this is the one for the Law of Momentum Conservation which says that the momentum before the collision of the balls has to be the same after the collision because momentum cannot be created or destroyed. For us in particular:

and filling in:

[(4.0)(6.0) + (2.0)(0)] = [(4.0 + 2.0)v] and

24 + 0 = 6.0v and

24 = 6.0v so

v = 4.0 m/s to the right

6 cos 34, 6 sin 34 trig