# Problem Understanding Physical Pendulum

1. Sep 26, 2007

I am having trouble understanding what h is in the equation for T listed below. Here is an image

The Problem: A physical pendulum consists of a uniform circular disk (of R=2.35cm) supported in a vertical plane by a pivot located a distance D=1.75cm from the center of the disk. The disk is displaced by a small angle and released. What is the period T of the resulting SHM?

Equations:
$$T=2\pi\sqrt{\frac{I}{mgh}}$$

$$I=I_{cm}+mH^2$$

from text $$I_{disk}=\frac{1}{2}MR^2$$

This is where I am messing up either my algebra or what I am interpreting as h.

For the parellel-axis theorem I had $$I_{disk}=\frac{MR^2}{2}+MD^2$$ where D is the distance from the COM to the pivot.

and for h in mgh I thought the total height was h=D+R.

Am I correct about what h is? Or no? This will determine what my mistake is:yuck:

Thanks
Casey

Last edited: Sep 26, 2007
2. Sep 26, 2007