In sci.environment, Eeyore
>
wrote
on Sun, 30 Dec 2007 10:19:18 +0000
>:
>
>
> Kurt Lochner wrote:
>
>> AKA sniveled ineptly:
>> >
>> >The new gas mileage standards mandated
>> >by the recently passed energy legislation
>> >defy the laws of physics..
>>
>> leotard, you don't know any physics to speak of..
>
> The laws of physics certainly do tend to say that expecting a 7 litre
> V-8 (or even say a more humble 4 litre) to do 35 mpg is wishful thinking
> ! But who actually NEEDS one ?
>
> Graham
>
Who needs a car to begin with? :-) But given that, I'd
be surprised if one can do 35 mpg in an SUV form factor,
even with the most efficient of engines. If one assumes
stoplights every 500 m and a driving speed of 15 m/s, a
2-tonne car needs to spend 225 kJ just getting up to
speed, and then waste that 225 kJ stopping (unless one uses
regenerative braking techniques), translating into 450 J/m
or 724204.8 J/mile or 167 mpg (given gasoline's energy density
of about 121 MJ/gallon) -- and that's without air drag,
rotational friction, and Carnot inefficiencies.
The solution, of course, is to shrink the car and use
lighter materials. Ideally, every family of 2 kids
under driving age (around 16-18 years) would have three
cars:
- his car, which would be a tiny 1-seater with very high
fuel efficiency, optimized for commuting, and just
big enough to hold a briefcase and a cup of coffee.[*]
- her car, which would be a 1 to 3-seater with not quite
as high fuel efficiency but which can carry a week's
worth of groceries; it can also be used to pick up
and drop off kids from various functions, although
ideally the kids would use bicycles instead or just walk,
as both are healthier, if less safe in some neighborhoods,
depending on the age of said kids (obviously babies
crawling to the day care center or to Grandma gets
ridiculous, but there's a line somewhere).
- the family car, which would be a 4-seater primarily
intended for long trips and family outings, and it
sits in the garage most days.
(Switch roles as appropriate. There's a few issues if his
employment involves hauling [long haul truckers] and/or
building construction work. Not sure how to handle a visit
by his folks, her mother in law or by either Grandma --
or all of the above simultaneously during the winter
holiday season. Hopefully they have cars of their own.)
It is possible to change this mix somewhat, or add additional
components such as mass transit (trains, vanpools, light rail,
commuter buses).
[*] This is suggested with humorous effect by
_The Incredibles_, among many other venues. One would,
of course, want a little more durability so that it
can survive being gripped or slammed, of course.
--
#191,
Linux. Because Windows' Blue Screen Of Death is just
way too frightening to novice users.
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