Task: Text Categorization
Input (English): The gyromagnetic ratio of an electron is equal to the magnetic moment divided by this quantity. Its operator is equal to negative i h bar times r cross the gradient. The quantum number j corresponds to the total value of this. Its conservation is a consequence of the isotropy of space. Its derivative with respect to time is torque and Kepler's second law follows from it being conserved. It is equal to the product of moment of inertia and angular velocity. For 10 points, name this rotational version of momentum.
Output (English): Science