A woman with mass 50 kg is standing on the rim of a large...

A woman with mass 50 kg is standing on the rim of a large disk that is rotating at 0.80 rev/s about an axis through its center. The disk has mass 110 kg and radius 4.0 m. Calculate the magnitude of the total angular momentum of the woman$-$disk system. (Assume that you can treat the woman as a point.)

Transcript

00:01 So we're told a woman with mass of 50 kilograms is standing on the rim of a large disk that is rotating at 0 .8 revolutions per second.

00:10 So what we got, we got this disk like a merry -go -round or something rotating, and we have some woman standing on the edge of it here.

00:19 And so this thing is rotating, you know, around.

00:23 Well, it doesn't really matter which direction.

00:29 We basically, does it actually say no? because they ask us for the angle of momentum.

00:35 And the angle momentum will be basically in the right -hand rule direction of whatever we call positive here, or whatever direction it's, we'll say it's rotating.

00:47 Now the disk weighs 110 kilograms and has a radius of four meters.

00:53 So they ask us for the magnitude of the total system.

00:58 So that means the angular momentum, the magnitude of the angle of the momentum of the total system.

01:04 So that means we have two pieces.

01:07 There's various ways we could do it.

01:09 We could calculate a mass moment for the system as a whole, or we could just piece together the angle momentum in pieces.

01:18 So we can either piece together the mass moment or piece together the angle momentum.

01:23 Either way, we should get the same answer.

01:25 I just calculated the angle of momentum for each.

01:30 So the angular momentum of the woman is her mass times the distance from the axis of rotation times her velocity.

01:39 And so her mass is 50, the radius is 4...

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