Re: A Parents' Day gem

[Leigh Palmer <palmer@sfu.ca>]

> Leigh Palmer wrote:
> > (I thought John Mallinckrodt's observation about a retarding force
> > having a greater than first power velocity dependence providing
> > effective lift to be a revelation here. I'd never heard of such a
> > thing, but it is obviously true - and significant. It explains for
> > me why bullets fired from a rifle don't fall with acceleration g.
> > I have written an authority for information on this topic and I
> > will, of course, share it when I get it.)
>
> I am very much looking forward to this information.  The notion of the
> retarding force being proportional to v-squared is an approximation, and
> I have seen that approximation used only for calculating the force
> opposite to the direction of motion.  I wonder if the lift effect is a
> reflection of the data or only a case of a limited model being applied
> outside of its range of validity.

I think that v-squared dependence is not an issue here. The only issue
is whether the drag term for the vertically falling bullet is less than
the vertical component of drag for the horizontally fired bullet. This
is a question about objects which inevitably fall; they have downward
velocity components despite the brief horizontal motion.

I wrote a fellow in New Zealand. I'll let everyone know when I hear
from him.

Leigh