Answer:
Cart B loses some of its initial kinetic energy and cart A gains kinetic energy.
Step-by-step explanation:
Since both cart A and cart B have identical masses, and cart B moves with a smaller velocity after the collision than it was moving with before the collision, and also, the collision is elastic. It implies that the initial kinetic energy of cart B equals the final kinetic energy of cart A and cart B after the collision.
Since the initial kinetic energy of cart B is shared between cart A and cart B and cart B moves with lesser velocity after the collision, it implies that cart B has a smaller kinetic energy than its initial kinetic energy before the collision.
And also, since cart A is initially at rest and moves to the right after the collision, it gains kinetic energy.
Thus, cart A has a higher final kinetic energy after the collision. Also, cart A has a smaller kinetic energy after the collision than the initial kinetic energy of cart B, since it is the difference between cart B's initial and final kinetic energies.
So, from our observation, we conclude that cart B loses some of its kinetic energy and cart A gains kinetic energy.