# Angular momentum

## Explanation

In classical mechanics, the angular momentum is the rotational momentum of an object that is rotating about an axis. The object can also have spin angular momentum if it is spinning about its own axis. For an object orbiting around an axis, the angular momentum is mathematically described as a cross product of the object's position vector r and the linear momentum vector p. It is also described as the product of the angular velocity ω and moment of inertia I. In all the cases, when there is no external torque acting on the object, the angular momentum is conserved. For example, our Earth spins on its own axis as it revolves around the Sun in an orbit. In this case, the earth has both a rotational angular momentum and a spin angular momentum.