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Re: [Phys-l] truck mileage



Hi all-
Of course all such data need to be taken with a few grains of salt, and driving habits can play a major role in the result. But, consider the physics of a truck pulling a trailer at constant speed on a level road. Power required be the presence of the trailer is that dissipated by the rolling friction of the trailer wheels. How much does that friction increase when a load is placed obn the trailer? I don't have much feel for the numbers, but it must be a small fraction of the added load. The gal/mi is proportional to the friction force, which is probably proportional to some power of the speed. My conclusion is that in all likelihood, a small decrease in the speed could compensate for the added friction due to the increased load.
Regards,
Jack



On Wed, 7 May 2008, Bill Nettles wrote:

I agree the data are questionable

OR
the truck driver doesn't go as fast when he has 10000# of cows :)

Is there a baseline gas mileage with a nonlinear increase (arctangent) as the weight decreases? Gas mileages are notoriously non-linear for most variables.

Kathy Daniel <kcdohs@comcast.net> 5/7/2008 4:02 pm >>>

I have quite an interesting problem that I cannot explain...

Our Ag teacher set up this scenario for me:

one 5000# truck gets about 18 miles per gallon
same 5000# truck pulling a 4000# trailer gets 8 miles per gallon
same 5000# truck pulling a 4000# trailer + 10000# of cows ALSO gets 8
miles per gallon.

Any ideas why the empty and the full trailer both get the same
mileage? This same pattern is also present in a different trailer and
truck combination.

thanks,
Kathy


Kathy Daniel
Oakland High School
Murfreesboro, TN 37130
kcdohs@comcast.net

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Forum for Physics Educators
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https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l


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