## Yahoo! 2 years ago The moment of inertia of a thin sheet of mass m and radius R about AB ?

1. Yahoo!

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2. JamesJ

Use the parallel axis theorem

3. Yahoo!

I (AB) = I (CM) + m * perpendicular Distance

4. Yahoo!

Ryt

5. JamesJ

in other words, start with the moment of inertia of the disc rotated through an axis running through the center of the disc, then apply the theorem to shift the rotation axis.

6. JamesJ

Yes

7. Yahoo!

so mR^2 /4 + m R^2

8. Yahoo!

@JamesJ ??

9. JamesJ

No, the moment of inertia rotating a disc about its center axis is mR^2/16

10. Yahoo!

11. Yahoo!

17mR^2 / 16

12. Yahoo!

@JamesJ

13. JamesJ

Whats the perpendicular distance between the CM and the axis in this problem?

14. Yahoo!

R

15. JamesJ

No, the *perpendicular* distance

16. JamesJ

|dw:1360168373543:dw|

17. Yahoo!

|dw:1360168379873:dw|

18. JamesJ

We want the distance which is perpendicular to the axis of rotation, as I shown on my diagram

19. Yahoo!

Ok..i got it nw.....Thxxxx a lot

20. Yahoo!

Yup..i got it