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## Homework Statement

It's part of Kleppner and Kolenkow 7.4.

See the attached picture.

(The disk is rotating around the vertical "stick", not rotating towards it. (I have bad drawing skills)

The question mainly asks what is the normal force on the disk.

I am stuck trying to find the moment of inertia of the z direction.

## Homework Equations

[tex]\int r^2 dm[/tex]

## The Attempt at a Solution

I don't have much to go with.

Well, I said that the perpendicular direction from the disk is constantly R.

For dm, I was thinking thinking of dividing the disc into vertical slices so that they look like horizontal rods.

Then I simply did not what to do because I did not know how to set up the bounds on the integral.

So, the mass of one those segments should be [tex] \rho dL [/tex] with dL changing from 0 to 2b. and my integral should be times 2 since I have a top and bottom to my disk and from 0 to 2b is only one half.

But it just looked weird and I know it's wrong. So I really need help with this part.

[tex] \int_{0}^{2b} 2R^2 \rho LdL = 8R^2 \rho b^2 [/tex]