somewhere. than you
I think you're looking at the lorry & car as an isolated system, in which case you are perfectly correct in your buttertion of conservation of moment between the two.
I'd still maintain that the lorry is quite strongly coupled to the earth by the huge friction of it's tyres, and it's not rolling freely. The engine does indeed provide braking, and although the braking of an open throttle diesel isn't great, the size of a lorry lump is going to provide very effective braking against something the of the mbutt of a car. So the earth is going to gain some of that momentum.
We're also arguing about absolute figures on the buttumption that the differential speed is at least 40mph. If the car is hit in the right way (or the wrong way, depending upon your POV) it is perfectly possible that an immense amount of damage would happen to it at a much lower speed when coming into contact with a much larger object.
I'm with you on the point that the lorry driver must have felt something, but this might have easily been confused with something else - going over debris, etc.
Cruise Control dangerous 5269I have consistently included the earth, but admit to being unsure of how much momentum could be lost to that, and what the limiting factors...
-- Richard Sampson
mail me at richard at olifant d-ot co do-t uk
