For 10 points, name this quantity conserved according to the rotational analogue of Newton's second law.
The addition of these quantities is governed by the Clebsch-Gordan coefficients. This quantity is the rotational Noether two-charge, so it is conserved by systems with rotational invariance. Given in general by the wedge product of the displacement and the linear version of the same quantity, or the moment of inertia times the rotational velocity, this quantity's time derivative is the torque. One device that exploits this quantity's conservation is the gyroscope. For 10 points, name this quantity conserved according to the rotational analogue of Newton's second law.
The addition of these quantities is governed by the Clebsch-Gordan coefficients.
{angular momentum} [grudgingly accept {rotational momentum}; prompt on {L}; do not accept or prompt on “momentum”]