Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC, wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really isn't
a large loss unless you're playing for real small power such as that
developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ρ A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
ρ = Density of fluid (liquid or gas), kg/m3. (dry air at 70 degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge. KE = ½mv²

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston


You both missed the V^2 in the equation. To go 1.6 times as fast requires
2.56 times as much force and around 4 times as much power.

PS: you also missed converting the 30 sqft to square metres.