The law of conservation of angular momentum states that the total angular momentum of a system remains unchanged in the absence of external torque. This law is fundamental to physics and applies to all isolated systems. Isolated means that interactions have occurred without interference from the surroundings.

One common example of this law is ice skaters. When a skater pulls in his arms while spinning, his moment of inertia decreases. To conserve angular momentum, his rotational speed increases, causing him to spin faster. This phenomenon is also evident in figure skating, where extending the arms slows down the spin, while pulling them in accelerates it.

The other is in space with astronauts. When an astronaut throws something away, he starts rotating in the opposite direction. This reaction shows that the conservation of angular momentum applies because neither the astronaut’s nor the thrown object’s combined angular momentum has changed.

In astrophysics, the formation of planets and stars from rotating gas clouds is an example of this principle. As these clouds contract due to gravity, their rotation speeds up to conserve angular momentum. Finally, when riding bicycles or motorcycles, leaning into a turn helps maintain balance, as the angular momentum of the bike-rider system remains constant while navigating curves.

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