On Mon, 24 Jul 2006 23:36:56 +0100, Dave Plowman (News) wrote:

In article ,
The Natural Philosopher wrote:
so if the numerator and denominator are both zero that works out at 1

Err no, 0/0 is not 1.

It is actually incalculable.

Surely anything divided by zero is infinity?

But surely zero divided by anything is zero? :-)

As TNP says it's incalculable (or meaningless or undef or NULL or whatever
you like to represent not-a-number). Perhaps more interesting and/or
useful is what happens as the ratio of useful work to total work tends to
zero. If I could remember anything of my school calculus I might embarrass
myself offering a mathematical analysis :-)

However in the spirit of Scroggie I'll attempt an arm-waving one instead.

Consider what happens at 1 mph, 0.1mph, 0.01mph etc. Assume there is no
wind and the vehicle is on a flat level surface. The losses due to air
resistance are miniscule, so we have basically rolling resistance plus
losses in the engine itself and its transmission. These probably do not
dimish with speed so the efficiency doesn't tend to 100% (although the
effeciency of the electric vehicle is obviously going to be hugely better
than the IC vehicle).