CONSERVATION OF LINEAR MOMENTUM Two masses are on a level surface. Mass B is initially at rest. Mass A is moving towards the mass B with a speed on 1.2 m/s. The masses collide head-on. (a) If mass A recoils with a speed of 0.3 m/s, what is the post-collision speed of mass B? (Use the sign convention for head-on collisions; let the forward direction be the "positive" direction, and the recoil direction be the "negative" direction. Let mass A be twice that of mass B. (b) Is the collision described above an elastic collision? Justify your answer by showing the calculations