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Conservation of angular momentum

Say if an ice skater spins with angular speed omega and moment of inertia I

L =(omega)(I)

Before the spin takes place the skater has 0 angular momentum. (1)
After the spin occurs the ice skater has a certain value of L. (2)

Would i be correct to say that the earth spins, so that in scenario (2) the total angular momentum before the spin happens = total angular momentum after spin happens, and earths spin is the contribution to this?
Original post by Zenarthra
Say if an ice skater spins with angular speed omega and moment of inertia I

L =(omega)(I)

Before the spin takes place the skater has 0 angular momentum. (1)
After the spin occurs the ice skater has a certain value of L. (2)

Would i be correct to say that the earth spins, so that in scenario (2) the total angular momentum before the spin happens = total angular momentum after spin happens, and earths spin is the contribution to this?


Yes. You have to take into account the whole system, which includes the Earth. Of course the Earth is so large that the very tiny change in its motion would be undetectable.

Exactly the same argument applies to linear momentum.
When a car crashes into a wall, its momentum has to go somewhere. In this case it would cause the Earth (attached to the wall) to change its motion by an imperceptible amount. The momentum of the system car plus Earth remains constant before and after the collision.
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Original post by Stonebridge
Yes. You have to take into account the whole system, which includes the Earth. Of course the Earth is so large that the very tiny change in its motion would be undetectable.

Exactly the same argument applies to linear momentum.
When a car crashes into a wall, its momentum has to go somewhere. In this case it would cause the Earth (attached to the wall) to change its motion by an imperceptible amount. The momentum of the system car plus Earth remains constant before and after the collision.



Ahh ok, thank you.

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