- #1

whitetiger

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## Homework Statement

http://img120.imageshack.us/img120/808/periodicemotionhd3.jpg solid, uniform disk of mass M and radius a may be rotated about any axis parallel to the disk axis, at variable distances from the center of the disk

**If you use this disk as a pendulum bob, what is T(d), the period of the pendulum, if the axis is a distance d from the center of mass of the disk?**

and

The period of the pendulum has an extremum (a local maximum or a local minimum) for some value of d between zero and infinity. Is it a local maximum or a local minimum?

## Homework Equations

From the picture, I come up with the moment of inertia of the solid disk around its center of mass

I = 1/2Ma^2

From the question, we are asked to find the period of the pendulum if the axis distance d from the center of mass.

The period T for this is P= 2pi (sqrt L/g) where g is the gravitation force

and L is the lenght.

From my understanding is that because of the new lenght, we need to use the Parallel Theorem to find the new lenght

I am not sure about this, so hope someone can help

Iend = Icm + Md^2

Iend = 1/2Ma^2 + Md^2

So the period is P = 2pi (sqrt(( a^2 +d^2)/g))

But this is not correct.

Thank

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