# Homework Help: How odometer works ?

1. Oct 29, 2012

### haleh

How odometer works ??

I get a problem ,my university professor for physics 1 ask me to search about work of odometer in physical view ,I mean he doesn't want to describe the mechanical or electronic odometers !!he wants me to write physical formulas and measure the distance which cars travel the same as what odometer does !!!and it should be at least 4 page . I some how search and I understand that electronic or mechanical ones measure the rpm of wheels and then convert this to kilometer or mile and this can be like this : number of revolution * radius of wheel * 2 * pi
but I some how confused that rpm is not number of revolution ,Is there any timer in cars???? or maybe I am completely wrong and my professor wants other things so what do you suggest me to search about ???and is there any link ,book you can suggest me ??? any idea ??

2. Oct 29, 2012

### SteamKing

Staff Emeritus
Re: How odometer works ??

Are you sure that a mechanical odometer measures rpm? Think about how it is constructed.

3. Oct 29, 2012

### haleh

Re: How odometer works ??

Hi SteamKing
you are right but my problem is that none of these relate to physics and my professor insists that he just wants physic formulas or s.th like this!!and it should be at least 3 or 4 pages !!what do you think he wants ???I am really confused ,these are so simple !!!

4. Oct 29, 2012

### haruspex

Re: How odometer works ??

Before 1900, odometers worked by counting revolutions. For those it was a simple matter of gearing down enough to be counting in the desired units.
Nowadays, the rate of rotation is measured and this drives both the odometer and the speedometer. For that, you need to be integrating the rate over time.
But to make that go 4 pages you'll have to use a large font.