What Is Momentum?
Linear momentum is mass times velocity: p = m v. It is a vector, with SI units kg·m/s (equivalently N·s).
Newton's second law in its original form reads F = dp/dt. For systems where no net external force acts, total momentum is conserved — one of the strongest constraints in mechanics. The conservation law follows from translational symmetry via Noether's theorem.
Examples: rocket propulsion, the recoil of a rifle, momentum transfer in Newton's cradle. In special relativity p = γmv with γ = 1/√(1 − v²/c²), and the conserved 4-momentum unifies energy and 3-momentum.
Recent research on this topic from arXiv
Preprints and papers indexed on arXiv.org. Links open the public abstract pages.
- Statistical and strict momentum conservation
Tian-Hai Zeng, Zheng-Zhi Sun, Bin Shao · 2020 ·arXiv:2001.06289v1
Arguments about the conservation laws of energy and momentum in the micro-world being statistical or strict began in 1924, and conflicting viewpoints remain today. The former is mainly supported theoretically, but the latter has been proved... - Momentum Conservation at Small x
R. D. Ball, S. Forte · 1995 ·arXiv:9507321v1
We discuss how momentum conservation is implemented in perturbative computations based on expansions of anomalous dimensions appropriate at small $x$. We show that for any given choice of $F_2$ coefficient functions there always exists a fa... - Position Measurements Obeying Momentum Conservation
Paul Busch, Leon Loveridge · 2010 ·arXiv:1005.0569v3
We present a hitherto unknown fundamental limitation to a basic measurement: that of the position of a quantum object when the total momentum of the object and apparatus is conserved. This result extends the famous Wigner-Araki-Yanase (WAY)... - Electromagnetic Momentum Conservation in media
Iver Brevik, Simen Å. Ellingsen · 2010 ·arXiv:1007.4403v1
That static electric and magnetic fields can store momentum may be perplexing, but is necessary to ensure total conservation of momentum. Simple situations in which such field momentum is transferred to nearby bodies and point charges have...