On Oct 8, 9:16 am, Nige Danton wrote:
On Oct 8, 3:03 pm, Nige Danton wrote:

On Oct 8, 2:58 pm, Adrian wrote:

within any given class are likely to be fairly similar. As a rough rule
of thumb, increasing drag starts to come seriously into play from about
60mph upwards.

Drag cubes with velocity and so it may become important at speeds
lower than 60 mph.

My response would have been better phrased as "drag cubes with
velocity; are cars really so slippery that drag does not become
significant until 60mph?"

I *think* that the force exerted by drag goes as the /square/ of the
speed. That means the energy (and hence fuel consumption) per unit
distance will also go as the square. I suspect what you are thinking
of is that the /power/ (energy per unit time) is force * distance /
time which is force * speed, and hence the power used by drag goes as
the cube of speed.