3 ms·
"...moving twice the speed takes 4X the energy..." That's not quite right. The power required to maintain a constant velocity v against a constant drag force o
by troymc 3y ago
"...moving twice the speed takes 4X the energy..."
That's not quite right. The power required to maintain a constant velocity v against a constant drag force of F is P = Fv. With air drag on a car moving at highway speeds, the drag force F actually depends on v: it's proportional to the square of v, i.e. F ~ v^2. All together then:
P ~ v^3
So doubling the speed will increase the required power by a factor of eight.
- sebzim4500 3y agoAren't you agreeing with him? If the power is 8x higher and the speed is 2x higher then the energy per mile must be 4x higher, as he says.
- ooterness 3y agoPower is energy power unit time. You are correct that power lost to aerodynamic drag increases with the cube of velocity. However, if you increase speed, the time spent is reduced. As a result, the total energy grows with velocity squared.