Answer:
2)Kinetic energy of the system is partially used up in the deformation of the vehicles.
Step-by-step explanation:
The collision described in the problem is a type of collision which is called "perfectly inelastic collision". In a perfectly inelastic collision, only the total momentum of the two objects colliding is conserved, while the total kinetic energy is not. In fact, in a perfectly inelastic collision the two objects stick and move together after the collision: since the two objects stick together, part ofthe total kinetic energy is converted into heat due to the frictions between the surfaces of the two objects.
Therefore, the correct answer is
2)Kinetic energy of the system is partially used up in the deformation of the vehicles.