On Fri, 16 May 2008 21:11:34 +0100, Orchid XP v8 wrote:

>>> If I put my car into top gear and set the engine to 3,500 revolutions
>>> per minute, my car travels forward at almost exactly 75 miles per
>>> hour. So... how far forward does it travel for a single revolution of
>>> the engine??
>> 
>> Is this a math puzzle, or a real question?
>> 
>> If it's a real question, it's almost impossible to answer from the
>> information given.  You have to take into account acceleration,
>> momentum, friction, etc.
> 
> How so?
> 
> The engine is directly coupled to the wheels. Unless the car looses
> traction, the forward motion of the car and the rotational speed of the
> wheels and engine all have a simple linear relationship.

There isn't a linear relationship between the rotational speed of the 
wheels and the speed of the engine.

If I take my foot off the gas, the engine revs drop.  The car may or may 
not slow down (depending on the road and the landscape).

Similarly, if I apply the brakes to a full stop, the engine doesn't die, 
it idles.

Then of course if you put the car in neutral, you've completely 
disengaged the engine from the wheels.

Jim

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