Final answer:
Momentum is conserved in a collision involving a ball and a wall anchored to the Earth when the system is defined to include both the ball and the Earth. The Earth's large mass ensures that its recoil is minimal but non-zero, conserving the total momentum of the larger system.
Step-by-step explanation:
When considering if momentum is conserved during a collision involving a ball and a wall anchored to the Earth, the correct answer is A. Yes, momentum is conserved. To understand this, we have to define our system as not just the ball but the ball plus the Earth. While it might seem that the Earth's reaction is negligible due to its large mass, it does recoil slightly, ensuring that the total momentum of the system remains constant. This principle applies to any collision if we consider a system large enough to include all interacting bodies.
For example, two objects with equal mass colliding and one comes to rest while the other moves with some velocity signifies that momentum is conserved, but we cannot be certain that kinetic energy is conserved without additional information about the velocities after the collision. Similarly, when a ball is hit by a racket, the momentum of that system is conserved if we consider the momentum changes of both the ball and the racket, and by extension, the player holding the racket.