# Re: Repeal of the National Speed Limit Law

```In article <3t6k19\$pph@library.erc.clarkson.edu> jet@sun.soe.clarkson.edu (Jeff Thompson) writes:
>   Um,  I don't think so.  Since slowing the car down involves
>dissapating the kinetic energy of the car, and KE = 1/2 mv^2.
>That is why stopping distances increase exponentially, not linearly
>with speed.
>[snip]
>  Therefore it you have to dissapate 40% more energy to slow
>from 75 to 65 than from 55 to 45.  And assuming that you
>have the same constant energy removal rate (no brake fade)
>in both cases, you would also travel more than 40% farther since
>problem in most cars, that will only make things worse.

Except you also need to consider that wind resistance is proportional to v^3.
So one gets substantial help from wind resistance when slowing from 75 to 65
mph.  I would attempt to quantify this like you did, but that would require
solving a differential equation, which I've refused to solve even since I was
scared silly as an undergraduate when I solved on and got a Bessel function.
;-)

With my car, I can slow down fairly quickly from 75 mph to 65 mph simply by
taking my foot off the gas pedal.

>  Not meant as a flame or personal attack, but stuff like this
>is one of the best arguments *not* to raise the speeed limit.
>There are too many people who have no idea of how to deal with
>the incerased stopping distances and how the car is going to
>behave.

I would postulate that people learn empirically how their car behaves in
braking from various speeds by trying it.  After a while, they get a "feel"
for how their car behaves in most situations.

> I don't really think that the majority of drivers are
>stupid, but they are certainly woefully undertrained and
>undereducated.

Well, surveys have shown that 80% think they are above average.  ;-)

However, I think the distribution of driving skills follows a binomial
distribution, as follows:

manics   -    50%
idiots     -    50%

;-)

Regards,
Andy

--
_____________________________________________________________________________
Andy Gough                      |      "Knowledge is power."
Internet: agough@primenet.com   |                -- Francis Bacon
ICBM: 33^18'29" N  111^48'39" W |
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```

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