Re: Shayne AVERAGED 108 mph?!

[James Marriott <marriott@micron.net>]

Haudi,

> >The thing  to remember on German roads, is that if you are travelling at
> >120mph,
> > and a brit with a caravan doing 50 pulls out in front of you, it is the
> >equivalent
> > of stopping dead from 70mph.
> 
> Wouldn't this only be true in a vacuum? Something about aerodynamic drag
> increasing
> with the square of velocity? (help me out, here).

Correct. Aerodynamic drag _force_ increases with the square of the
velocity, which means aero _power_ (force * velocity) increases as the
cube of velocity. So, the Hp required to go, say, 120 MPH is 73% more
than that required to go just 100 MPH. Funny, eh? Well, maybe not so
funny in the 4kq (115 PS, Cd ~ 0.9).

The big mis-perception here is that, even though aero drag is helping a
little to slow the car, braking "effort" is quite non-linear. That is,
due to kinetic energy going as the square of velocity, slowing from 120
to 50 generates 2.43 times the heat (aero "help" neglected) that
stopping from 70 would. (  (120^2 - 50^2)/70^2  )

cu on the boost-o-bahn and back to your RS non-dork programming,
James
'87 4kq
'89 200q