Centre-of-mass dynamics
External force controls the mass-weighted centre's acceleration.
Key knowledge
For fixed-mass Newtonian particles with cancelling internal force pairs, the centre of mass R is the mass-weighted position and M R̈ equals total external force.
Values and equations
M = Σ_i m_i; R = Σ_i m_i r_i / M; M R̈ = F_ext
- M, m_i
- Total and constituent masses kg
- R, r_i
- Centre and constituent position vectors m
- F_ext
- Net external force N
Conditions and scope
- Use an inertial frame, fixed constituent masses and M > 0.
- Matter flow through a boundary requires additional momentum-flux terms.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Section 9.6, equations 9.25–9.33: system force sum and mass-weighted position.
2026-10-10 · Fixed-particle centre-of-mass balance only; no variable-mass rocket equation.
Entry details
Permanent link to this entry ↗- Record identity
- physics-centre-of-mass-balance
- Revision
- university-reference.1
- Structured reference record
- University reference · University core expansion