00:01
Alright, so let's say we have an ice skater with a moment of inertia, an initial moment of inertia of 0 .36 kilograms times the square meter, and they have an initial angular velocity of 6 .6 revolutions per second.
00:19
And so we want to, first let's write that, 41 .47 radians a second.
00:25
We're told they pull their arms outwards until they have a rate of rotation of basically 3 pi radians per second.
00:35
So we want to calculate, first off, their initial angular momentum, which is li, so this is the moment of inertia times the initial angular velocity.
00:46
And so that's 14 .93 kilograms times the square meter per second.
00:54
And then part b, we want to find their moment of inertia after they pull their arms in.
00:59
So if is going to be the initial angular momentum divided by the final angular velocity.
01:04
So this is about 1 .584 kilograms times the square meter...