# Homework Help: Fermi Numbers?

1. Sep 28, 2004

### Faiza

Fermi Numbers!??

I'm trying to solve this problem and explain all my steps in my reasoning.

If anyone can help me figure this out, reply
faiza

2. Sep 28, 2004

### Faiza

No Replies :( :'(

3. Sep 28, 2004

### Faiza

:"( ...............................

4. Sep 28, 2004

### Claude Bile

No of hairs on head is equal to;

No of hairs per unit area x Surface area of head with hair.

You need to get a value for both of these quantities, either through measurement or estimation (or both).

Claude.

5. Oct 1, 2004

### Faiza

this is hard lol

6. Oct 1, 2004

### Gokul43201

Staff Emeritus
Using the average diameter of a hair (about 50 microns, or pluck a few hairs and measure them) you can determine a rough upper limit on the number of hairs. The actual number depends on the packing density, which I think, is not likely less than 10% coverage. So that gives you an approximate lower bound. Pick the mean to get an order of magnitude estimate.