# Homework Help: Physical Pendulum Problem

1. Nov 14, 2009

### Jimmy25

1. The problem statement, all variables and given/known data

A uniform disk of radius R = 1.40 m and a 6.0 kg mass has a small hole a distance d from the disk's center that serves as a pivot point.

What should be the distance d so that this physical pendulum will have the shortest possible period?

2. Relevant equations

T = 2π$$\sqrt{\frac{I}{MgL}}$$

3. The attempt at a solution

Using the parallel axis theorem and moment of inertia of a disk I found the period as:

T = 2π$$\sqrt{\frac{\frac{1.4^{2}}{2}+d^{2}}{9.8d}}$$

When I find the minimum of this function I get d = 0.990 which is the right answer.

What I don't understand is why the d isn't zero. Won't T approach zero as d approaches zero?

Last edited: Nov 14, 2009
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