3. A 3-kg block moving 4 m/s to the right collides with an 8-kg block moving 2 m/s to the left.
a) If the two blocks stick together, what is the final velocity?
b) If the two blocks collide elastically and the 3-kg block moves to the left at 1 m/s, what is the final velocity of the 8-kg block?
c) How much kinetic energy is "lost" in the collision in a)?