On Fri, 11 Mar 2005 21:52:37 -0000, "Clive George"
No, they would have to slip relative to the ground they were rotating over - that is, rotate more slowly than the vehicle speed demanded. The resultant friction permits transfer of momentum.
Yes, I think I see where you are coming from. At a constant speed and throttle opening, the engine is balancing the drag on the vehicle. Give the vehicle a push and the engine reacts against this because it does not want to go any faster. However, this braking force is very limited, especially on unthrottled diesels (which I believe use exhaust baffles to provide engine braking, presumably mostly inoperative except when the throttle pedal is fully closed).
I suspect I may have miscalculated the distance (and hence the time) over which a colliding car crumples and shortens as it hits the rear of the lorry, but not by much, and I still got an impulse to the lorry of nearly 4g. Even if you knocked that down to 1g perhaps, it's still a hell of a shove, and it's only increasing the engine and vehicle speed by 3%. Hard to see how the engine could supply that level of braking force.
Cruise Control dangerous 5267Which straight away should have alerted me to some sort of chicken-up, as it implies a deceleration to the car of 80g, which is a little...
-- Seen it all, done it all, can't remember most of it.
Mail john rather than nospam...
