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Originally Posted by brucepick
Its the cube of the airspeed.
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With a doubling of speed the drag (force) quadruples per the formula.
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So two times faster increases air drag four times? That's squared, not cubed. Two times two.
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Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times a [the] work in half the time requires eight times the power.
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Four times the force already figures in the double speed, why is the double speed considered twice? If you are keeping a constant time, then the distance is double and thus the power exerted over the same time increases by the cube.
80 mph for one hour uses 8 times (2x2x2) the power of 40 mph for one hour. That's a cube, but the distance (displacement) is double.
80 mph for 40 miles uses 8 times (2x2x2) the power of 40 mph for 40 miles (a fixed displacement or distance), but for half as long. 2x2x2x.5 is the same as 2x2. 2x2 is a square, not a cube.
To me that's logical. If I'm wrong, why does it make sense to me?
Peakster 
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