Final answer:
The subject of this question is Elastic collisions. Elastic collisions involve the conservation of both momentum and kinetic energy.
Step-by-step explanation:
The subject of this question is Elastic collisions. Elastic collisions involve the conservation of both momentum and kinetic energy. In the case of bumper cars with springs, the collision between the cars is elastic because the spring stores potential energy and then releases it as kinetic energy during the collision.