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Comment by jfengel | Hacker News Reader

That implies that air resistance is the overwhelming contributor at high speeds. Is that the case?

It's the majority, but overwhelming or not surprisingly appears to depend on car model, at least per some calculations someone on reddit ran [1].

I'd add though that rolling resistance tends to be higher, on average, in winter too. When there's often a bit of snow on the roads... Less so on high speed highways admittedly.

[1] https://www.reddit.com/r/askscience/comments/l2cq6b/comment/...

Oh yes, by so much.

Even at 30kmph it's already the majority of the resistance and it scales exponentially with speed so you can imagine how much it matters.

It scales quadratically with speed*

Those two things very different.

For most cars driving through air, at sea level, on planet Earth, at normal speed, the drag force F is proportional to the square of the speed (v^2).

That's not exponential because the speed (v) is not in the exponent. In fact, it's quadratic.

Corollaries: The power required to push the car at speed v will be proportional to Fv ~ v^3. The gas spent over time t ~ energy spent ~ power time ~ v^3 * time.

Yeah sorry for my bad memory, you're right to correct it.

Considering air resistance is proportional to the cube of the speed, it would be highly surprising to not be the case.

It goes with the cube in terms of power, but with the square in terms of energy/distance, which is usually what you'd care about.

s/cube/square/

Define ‘high speeds’. There’s a reason race cars look like they do, to the point of having serious problems driving at speeds just a bit below highway speed limit.

Yes it is.

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