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In article <Pine.SGI.3.91.950329085251.21144A-100000@server.uwindsor.ca> Maisonneuve  Michael Jaso <maisonn@server.uwindsor.ca> writes:
>From: Maisonneuve  Michael Jaso <maisonn@server.uwindsor.ca>
>Subject: School Science competition!!!  Please Read...
>Date: Wed, 29 Mar 1995 14:06:14 GMT

>Ladies and Gentlemen, 

>I have here what I can discribe only as a brutal science competition.  
>This is the only event in which our school has decided to go out and look 
>for serious help in.

>Any help at all, suggestions, advice, tips...etc.  Will be appreciated.

>The event is called "Massing a Car."

>We will be presented with a car on a concrete floor in an auto shop and 
>given a maximum of 10min to determine the mass of the car in Kg.
>The car may be loaded unevenly (i.e., the weight of the car may not be 
>equally distributed on the 4 tires).  The tires may or may not be of the 
>same type (tread design, diameter, circumference, width etc.)
>The car will remain locked during the exercise.  We may not lift the car 
>in any manner, manually or mechanically.  We may not use any balances to 
>measure the mass or the weight of the car directly.
>We may measure any external features of the car (such as length, width, 
>height, tire pressure, tire dimensions, etc.).  (We must bring our own 
>measuring devices.)
>Scoring is based on how close to the actual mass of the car as determined 
>by the judges.  Ties will be determined by the shortest time taken to 
>complete the task.

>I can state that from previous years, time is of the essence!

>I have given all of the information we know and would appreciate any 
>responces.  

>The date of the competition is April 29, 1995.

>I will do my best to read the newsgroups I have posted this in as often 
>as possible but unless you want to discuss an idea among others E-mail 
>would be appreciated.

>Thanks in advance for anyhelp...

>Sean "Demetrius" Stephens
>maisonn@server.uwindsor.ca

>P.S. This is a high school competition in windsor ON, Canada.


If you consult the Ontario Reg. 741/81 or Ont. Driver's handbook (Page 72) 
you'll see that they should present you almost no tire mixtures unless they 
are equivalent by tire industry standards. (At least from the law's point of 
view) 

Having the same tire type (at least on each axle) would only spare you from 
measuring 2 tires. Although I've seen some suggestions posted to measure only 
one and multiply with 4. I remind you that ALL modern cars have a much bigger 
load on the front axle than on the rear one. So, in any case You'll have to 
measure at least one on each axle. 

From their specs it seems that the only way to measure has to do with tires 
and pressure. I also diagree with the articles that suggest you to measure the 
acceleration (inertia). 

The only thing that came to my mind is measuring the distance between the 
concrete floor (I think that's why they've mentioned concrete) to the CENTER 
of the wheel vs. tire pressure (use the same (precise if possible) gage in 
your tests at home and in the competition). 

If you're allowed to let some air out from the tires then the problem of 
different tires is solved. You measure the distance before and after you have 
evacuated some air. You'll find a good relationship between the mass on the 
wheel and the height difference if  you lower the pressure by a constant 
amount.

Building a mathematic model would take too much time and you always forget to 
take in count some data, so I'd suggest you go to the visitors parking and 
flatten all the tires. If you don't get caught you'll get an A at the 
competition. ( just don't loose your sense of humour).

Now to be serious, I think that if you'll try a few different cars (a 
japanese, a mid class modern and a big old Buick) you can draw some graphs 
that will allow you to guess within a good approximation.
The rest, I beleive is ... Good luck!

Adrian,

ajadic@chem.utoronto.ca