help with a physic-math question?

Question

the rubber worn from tires mostly enter atmosphre as pollution. Estimate how much rubber (kg) is put into the air in US every year. An estimate for a tire tread's depth is 1 cm when new and the density of rubber is about 1200 kg/m^3

Answer 1

Transportation’s MOBILE 6.2 model, used by regional governments to model air quality, uses a fleet average (all cars, old and new) of 20.3 mpg.
http://www.carbonfund.org/site/pages/carbon_calculators/category/Assumptions/

U.S. Department of Transportation Statistical Records Office reports there are approximately 62 million registered vehicles in the U.S. Stats accurate as of 02/01/05.

MOBILE6 shows an annual average mileage of close to 12,000 miles per year for passenger cars, and over 15,000 miles per year for light trucks

We'll use an average of 13,000 miles per year for all 62 million vehicles.


According to the U.S. Department of Transportation, average tire life is 41,000 miles.

I will assume that the Toyota Camry is the average tire width of
215 mm , or .215 m

The rim diameter is 16 inches and the profile is 60 mm, for a total diameter at the tread is about .56 m. Since there are 4 tires on the car, all will be multiplied by 4.

Based on the statistics for average miles driven and average tread life, the percentage of tread worn of a tire in the US is
100%*13000/41000
31.7 % per year

the tread volume lost per tire is
.215*.56*pi*.01*.317
.0012 m^3

the average total volume then is
.0012*4*61,000,000 m^3
292,800 m^3

So the mass is
292,800*1200
or
351,360,000 kg

j