# Angular Momentum Question?

Angular Momentum Question???

## Homework Statement

Figure 11-45 (attached) shows a rigid structure consisting of a circular hoop of radius R and mass m, and a square made of four thin bars, each of length R and mass m. The rigid structure rotates at a constant speed about a vertical axis, with a period of rotation of 2.5s. Assuming R=0.50m and m=
2.0kg, calculate (a) the structure's rotational inertia about the axis of rotation and (b) its angular momentum about that axis.

## Homework Equations

I=$$\int$$r2dm
L=I$$\omega$$

## The Attempt at a Solution

(a) I did mr2 = (10)(.5)2 = 2.5 (the answer is supposed to be 1.6
Then I tried msrs2 + mcrc2 = (8)(.25)2 + (2)(.5)2 = 1.5 (still incorrect)

(b) Due to not being able to solve "a" I could not began my attempt on "b"

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(a) I did mr2 = (10)(.5)2 = 2.5 (the answer is supposed to be 1.6
Then I tried msrs2 + mcrc2 = (8)(.25)2 + (2)(.5)2 = 1.5 (still incorrect)
Not sure what you're doing here. The thin rods and the hoop are standard shapes--you can look up their rotational inertia. (You'll need to use the parallel axis theorem.)

first find I of hoop along any diameter using perpendicular axis theorem and then use parallel axis theorem to find I along axis of rotation
do same for square

then just simply add their I

Thanks. I got it.