In an isolated system, which of the following is not equivalent to the momentum conservation law?

In an isolated system, momentum conservation law states that the total momentum of the system remains constant, provided no external forces act on it. The correct answer indicates that "p = 0" does not equate to the momentum conservation law because it represents a specific scenario where momentum is zero rather than a general principle applicable under varying conditions.

In contrast, the other options directly relate to the principles of momentum conservation. The expression "p = mv" defines the momentum (p) of an object in terms of its mass (m) and velocity (v), showcasing how momentum is calculated. The equation "F = dp/dt" describes the relationship between force and the rate of change of momentum, indicating that a net external force causes a change in momentum. Lastly, the statement "p_initial = p_final" encapsulates the conservation of momentum principle, emphasizing that the total momentum before an interaction (p_initial) equals the total momentum after the interaction (p_final) in an isolated system.

Thus, stating that "p = 0" does not represent a universal form of the momentum conservation law, which is why it is the choice that does not align with the law's principles.