Relativistic angular momentum can be compactly abbreviated in tensor index notation where the indices "i" and "j" take the values 1, 2, 3. On the other hand, the components can be systematically displayed fully in a 3 × 3 antisymmetric matrix This quantity is additive, and for an isolated system, the total angular momentum of a system is conserved. In classical mechanics, the three-dimensional quantity for a particle of mass "m" moving with velocity u has the dimensions of "mass moment" – length multiplied by mass. It is related to the boost (relative velocity) of the centre of mass (COM) of the particle
Velocity Moments image formula_14, and similarly for formula_20. formula_21 introduces velocity into the equation as where formula_23 is the formula_18 coordinate of the centre of mass for the previous image, formula_25, and again similarly for formula_20. After the Cartesian velocity moment is calculated, it can be normalised by where formula_28 is the average area of the object, in pixels, and formula_29 is the number of images. Now the value is not affected by the number of images in the sequence or the size of the object. As Cartesian moments are non-orthogonal, so are Cartesian velocity moments, so different moments can be closely