Rigid-body inertia tensor
A tensor relates rotation to angular momentum.
Key knowledge
For a rigid body, the inertia tensor about its centre of mass gives rotational angular momentum L = Iω. Its diagonal entries measure squared distances from axes; off-diagonal matrix entries carry minus coordinate products.
Values and equations
I_ij = ∫ (r²δ_ij − r_i r_j) dm; L = Iω
- I_ij
- Matrix components of inertia kg m²
- r, r_i
- Position and components relative to the centre m
- δ_ij
- Kronecker delta
- dm
- Mass element kg
- L
- Rotational angular momentum kg m² s⁻¹
- ω
- Angular velocity rad s⁻¹
Conditions and scope
- Positions are measured from the centre of mass in orthonormal Cartesian axes.
- I changes components when the axes change; L need not be parallel to ω.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
MIT Lecture 26 pages 2–3: integrals and matrix; SICM 2.2: mass moments.
2026-10-10 · Tensor definition and centre-of-mass angular momentum only; product-of-inertia sign convention explicit.
Entry details
Permanent link to this entry ↗- Record identity
- physics-inertia-tensor
- Revision
- university-reference.1
- Structured reference record
- University reference · University core expansion