What relates the momentum change of two colliding objects?

The correct answer is based on the principle of conservation of momentum, which states that in a closed system, the total momentum before a collision is equal to the total momentum after the collision. This principle applies regardless of the types of collisions—elastic or inelastic—and does not depend on one object being at rest.

In any collision between two objects, the total momentum is conserved, meaning that any change in momentum of one object will be matched by an equal and opposite change in momentum of the other object. This relationship ensures that the overall momentum remains constant, allowing for the determination of individual momentum changes based on the initial conditions of the colliding bodies.

Understanding this concept is crucial for analyzing collisions, as it aids in calculating velocities after impacts and understanding how forces are transferred between colliding bodies.