The momentum form of Newton's second law is more general than force equals mass times acceleration because it also applies to systems with:

1. The familiar form assumes the mass stays fixed while the velocity changes. 2. Newton's second law stated in terms of momentum is more generally applicable. 3. It can be applied to systems where the mass is changing, such as rockets, as well as to systems of constant mass. 4. A rocket burns fuel, so its mass falls continuously as it accelerates. _Source: OpenStax College Physics for AP(R) Courses 2e (CC BY 4.0), Ch 8 'Linear Momentum and Collisions', sections 8.1-8.7_