> Oh, it *does* accelerate... just... not very much. I mean, if you point a 
> *bicycle* downhill, it takes off like a rocket. And it doesn't even weigh 
> much! But a much heaveir car... doesn't seem to pick up speed very much.

If there was no friction the car and the bike would accelerate at the same 
rate, however cars have a lot more friction in the wheel bearings, tyres etc 
because they are heavier by a factor of like 20.

BTW did you actually try the experiment or is it just what you imagine?  It 
feels a lot faster doing 30mph on a bike than 30mph in a car!

>> Ermm, my car moves just by lifting the clutch gently, no need to rev at 
>> all.
>
> Is your car diesel by any chance?

Yes, but even petrol cars can do this - you just can't lift the clutch as 
quickly because the flywheel is usually much lighter in petrol cars.  Try 
it - you only need to give it some revs if you want to move off relatively 
quickly.

> Right. So given that there's roughly 10^3 revolutions per minute, that 
> would be about 10^(-3) L per minute. ;-)

Still not right, you can't use 1 mL of fuel per minute at 75 mph, otherwise 
you'd be able to drive for 5 weeks continuously without refilling!  Using 
something like 100-150 mL/min of fuel seems much more likely for a normal 
car at 75 mph.

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