In elastic collisions, both kinetic energy and momentum are conserved, which is crucial for solving problems involving masses in motion. The discussion raises a question about the direction of movement for a 2M block after a collision, suggesting confusion about its behavior. The participant emphasizes the need to apply conservation laws to derive equations for the velocities of the involved masses. The conversation indicates a challenge in understanding the implications of these conservation principles in specific collision scenarios. Ultimately, clarity on these concepts is essential for accurately analyzing collision outcomes.