12. (Center of Mass and Linear Momentum) A 3.2 kg box slides on a hor- izontal frictionless table and collides with a 2.0 kg box initially at rest on the edge of the table, at height h = 0.40 m. The speed of the 3.2 kg box is 3.0 m/s just before the collision. If the two boxes stick together because of packing tape on their sides, what is their kinetic energy just before they h strike the floor? Answer: KE = 29 J