Transcript for What is the conservation of angular momentum?

The Tabletop Expaliner; episode four - What is the conservation of angular momentum?

Nature conserves spinning.

Here a person stands on a turntable capable of turning parallel to the ground.

He is holding a spinning wheel perpendicular to the ground and at first he does not spin.

However, when he rotates the wheel, making it spin parallel to the ground,

the turntable starts spinning in the opposite direction

of the wheel to maintain (that is, conserve) the zero horizontal spinning we started with.

As he turns the wheel over, the turntable changes direction again,

the wheel’s spinning always canceling out that of the man holding it.

You might notice that the man doesn’t spin as quickly as the wheel.

This is because his spinning counts for more because he is more massive.

Essentially, there’s more stuff spinning.

However, nature doesn’t only care about mass when spinning is concerned.

Distance matters too.

Here a skater brings her arms inward and we notice she turns faster as a result.

This is because the large circle spinning counts for more then the small one.

So nature in an effort to balance the books, speeds her up.

Scientists call this spinning “thing” angular momentum, and there’s a fixed amount of it in the cosmos.

In fact, angular momentum plays an important roll in astronomy,

explaining why this binary star collects debris from its neighbor in a rotating disk.

To review, there’s this thing called angular momentum, and it cares about three things: how fast something's going; how massive that thing is; how big a circle it traces.

Do you have a question? Ask the explainer. explainer@davidcolarusso.com