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Old 01-10-2013, 01:38 PM   #23 (permalink)
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Location: Oakland, CA
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Big Orange Work Truck - '83 Ford F-250
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Originally Posted by christofoo View Post
Ever since I saw this data I've been wondering how compacts can be so crummy.
I wish they did better. I don't really want a mid-size, with the exception of the Prius mid-sizes all have 2.2-3L engines, which are blah for MPG.
I suspect a part of it is that a large percentage of very small cars are sports cars, and by virtue of being sports cars, they are more likely to be driven recklessly, especially (but not limited to) speeding.

This part was is a mistake however; "The affect of mass gets divided by two. A 4000 lb SUV will not absorb twice as much energy as a 2000lb car, it will only absorb 50% more."

Energy is linear with mass, so doubling weight does indeed double energy. The one-half term is a scalar, but the function remains linear (and proportional).
You're right, thank you for pointing that out. Its been a long long time since physics class. I'll fix it.

Energy is the not exactly the right parameter for safety WRT mass anyway. The key is whether your momentum will be changed by other the vehicle, or you will change the momentum of other vehicle.
I know, but there isn't any simple formula to describe that, and in order to make complex concepts understandable to the public (and when I write, I'm more writting to the general public than to hardcore modders) its got to be simplified to some extent.

This follows your percentage of the share of total mass.
not even just that - relative velocities (not just speed, but direction) - factor in as well. A semi-hitting a car causes fatalities at less than half the rate of cars hitting semis, for example, even though both cases have the same percentage share of total mass.

Originally Posted by Piwoslaw View Post
A few months ago I returned home just as my neighbor pulled into his driveway. It was cold (around freezing) with some rain and sleet, and he yells to me: You rode your bike? In this weather?!?

So the other day we both returned home at the same time again, only now the weather is warm, sunny, with no wind. And I yell to him: You took the car? In this weather?!?
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