Explaining conservation of angular momentum

Angular momentum is the quantity of rotation of a body, which is the product of its moment of inertia and its angular velocity.

The moment of inertia ($I$) is a measure of an object's resistance to changes in its rotation, depending on the mass distribution relative to the axis of rotation.

The angular momentum ($L$) of an object can be calculated using the formula $L = I \omega$

The law of conservation of angular momentum states that if no external torque acts on a system, then the total angular momentum of the system remains constant.

In real-world scenarios, the conservation of angular momentum can explain phenomena such as why a figure skater spins faster when they pull their arms in. Reducing the radius decreases the moment of inertia, increasing the angular velocity to conserve angular momentum.

Another example is the rotation of planets and moons which continue to spin due to the conservation of angular momentum from the time of their formation.