Concept:
Collisions are categorized based on whether kinetic energy is maintained throughout the event.
• Momentum: Momentum is conserved in ALL types of collisions (elastic, inelastic, perfectly inelastic) as long as no external forces act on the system.
• Kinetic Energy (KE): In an elastic collision, there is no permanent deformation or heat generation, so the total KE before the collision equals the total KE after.
Step 1: Evaluate the characteristics of elastic collisions.
By definition, a collision is "elastic" if the total mechanical energy of the system remains unchanged. This implies that the internal forces during the collision are conservative.
Step 2: Identify the conserved quantities.
Since there are no dissipative forces like heat, sound, or permanent shape change involved in a perfectly elastic collision, the kinetic energy of the system is preserved along with the linear momentum. This makes Statement (A) correct.