(02-04-2018 12:26 PM)rotor Wrote: It's worse than that
...
The fluid resistance (and the amount of fuel we need to burn to overcome it) is not proportional to the velocity we travel at, it is proportional to the square of the velocity.
It's even worse than that!
The *force* to overcome drag is proportional to the square of the veolocity. That's right. The *power* required (or energy per second, or fuel burnt per second) is the force times the veolocity, which means the fuel burnt (per second) is proportional to the cube of the velocity.
But then again, if you go faster, you spend less time... so fuel burnt per second is proportional to the cube of speed, but fuel burnt per mile is proportional to the square of speed.
Most people plan their stops in terms of range ("I shall stop every 200 miles"), but some do in terms of time ("I shall stop every two hours"), so these should consider the cube proportion.