Re: Car acceleration

[Michael Bowen <fizzbowen@MINDSPRING.COM>]

At 22:22 2002/02/02, Herbert H Gottlieb wrote:
> I thought that this thread had petered out.
> However, at the risk of being called silly
> also, try this one out for size:
>
> According to Newton's second law,   f=ma
>
> Transposing,                        m=f/a
>
> Therefore, if you divide a force on a
> car by its acceleration after a stop sign
> you CREATE MORE MASS ??

If you interpret this equation too literally, you could "prove" that it is
impossible for the car not to be accelerating at all times, otherwise [a]
would go to zero and the mass would become undefined.

Since the mass of a stopped car is, with ordinary assumptions, a
well-defined quantity, one can see that this equation can be
misinterpreted. Another such misinterpretation is that it is responsible
for "creating more mass". Think hard about what m = f/a is really trying to
tell you, and when its application is appropriate.