Re: When Physical Intuition Fails

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

Brian Whatcott wrote:

> John Mallinckrodt wrote:
>
>  >... In the case we are discussing an elastic collision is
>  >strictly impossible even in theory as the Newtonian analysis makes
>  >clear.
>
> Hmmm.... how elastic does the substrate need to be in the
> transverse direction of translation for John to admit the possibility that
> an initial stretch of the substrate in the "forward" direction (and
> compression in the opposite direction), can return
> its stored energy to the rolling cylinder  as the translation proceeds?
>
> Perhaps visualizing a rubber membrane as the substrate might help
> the intuition here?
> Or am I missing some feature of the math model that must exclude
> the high mu, no slip case from realisation?

You raise an interesting point, but I am still compelled by the
result of the careful Newtonian analysis which makes no assumptions
about the nature of the contact force other than that it always be
provided *at* the level of the floor.  The resolution of this
(seeming) paradox is likely that, if one really had such a surface,
the dropped spinning object would *never* settle down to the "rolling
without slipping" condition.  Instead, you'd have something like the
ideal bouncing "super ball" that *forever* bounces, trading intrinsic
angular momentum for orbital angular momentum and vice versa as it
lurches first one way and then the other.

--
John Mallinckrodt        mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.