The 18-kg block A slides on the surface for which μk = 0.3. The block has a velocity v = 10 m/s when it is s = 3 m from the 12-kg block B. The unstretched spring has a stiffness k = 1200 N/m . Take e = 0.6. The coefficient of friction is the same for both blocks.

Arailroad car collides with and sticks to an identical railroad car that is initially at rest. after the collision, the total kinetic energy of the two cars is a) the same as before. b) half as much as before. c) one third as much as before. d) one fourth as much as before. e) twice as much as before.