Re: [Phys-l] long-jumping to the wrong conclusion

[brian whatcott <betwys1@sbcglobal.net>]

On 1/12/2012 12:16 AM, Bernard Cleyet wrote:
> On 2012, Jan 10, , at 08:51, John Denker wrote:
>
> > Here's another end-of-chapter exercise:  Quote:
> >
> >    If a person can jump a horizontal distance of 3.0 m
> >    on Earth, how far could the person jump on the
> >    moon, where the free-fall acceleration is g/6 and
> >    g=9.81 m/s^2?  How far could the person jump on
> >    Mars, where the acceleration due to gravity is 0.38g?
> >
> > When I first saw that, I thought it was nice.  The physics
> > of jumping is something the students can relate to.  This
> > does not even require going to the moon, because you can
> > simulate reduced gravity using a Peter Pan flying-wire rig.
>
> I, w/ no additional thought, report the most recent AJP issue  has an article on hoop jumping and relates to stored muscle energy, etc.
>
> I think it "may" relate to JD's discussion.
>
> bc thinks Atwood machine.
I see bc was bemused too. It was helpful to notice that the optimal 
launch angle around 44 degrees at 1 g, varies,
so that at zero g, the launch may be horizontal, and lacking asperities 
may go on for ever (maybe not quite for ever...:-)
but that at hi g, the launch angle grows more nearly vertical, until 
even so, the center of mass does not escape the launch tube - with 
applications to leg muscle propulsion.

Brian W