FTP, name this quantity that measures the rotational inertia of a mechanical system.
In quantum mechanics, these operators obey the commutation relation L sub i with L sub j equals one-half i epsilon i j k times L sub k, and addition of two of them is governed by the Clebsch-Gordan coefficients.  In classical mechanics, if the Lagrangian is invariant under SO(3) [ess-oh-three], this quantity is conserved.  For a particle in a circular orbit, its magnitude is m v r, and for a spinning body, it is given by I times omega.  Generally, its time derivative is the net torque, and it is defined as the cross product of position with linear momentum.  FTP, name this quantity that measures the rotational inertia of a mechanical system.
In quantum mechanics, these operators obey the commutation relation L sub
angular momentum