Re: [Phys-l] Water Slides.

[Brian Whatcott <betwys1@sbcglobal.net>]

Jack Uretsky wrote:
> In general, in problems involving a mass powered by gravity, the mass 
> cancels out.
>  			Regards,
>  				Jack
>
> On Thu, 16 Jul 2009, Brian Whatcott wrote:
>   
> > Simplifying the scenario at little more:
> >
> > Does a straight descending slide produce a greater effective force on a
> > constant mass
> > at the foot of the slide if the runout is a curve straight in plan view,
> > or if the runout is a tight helix in plan view?
> >
> > If the answer to this question is NO, STOP here.
> >
> > If the answer is YES, does the centrifugal force experienced in the
> > rider's frame,
> > depend on his/her body mass as well as radius and angular rate?
> > If the answer to this question is NO, STOP here.
> >
> > If the answer is YES, what accounts for the different centrifugal force?
> > Will this set the larger mass higher on the slide/tube's
> > semicircular cross section in the bend?
> > If the answer to this question is NO, STOP here.
> >
> > If the answer is YES, can this test be repeated with a
> > sovereign and a feather in vacuo?   :-)
> >
> > Thanks for responding
> >
> > Brian W
> >
> > Bernard Cleyet wrote:
> >     
> > > A heavier object exhibits greater X double dot (and X dot terminal)
> > > w/ drag than a lighter one, n'est-ce pas?  e.g. Guinea and feather?
> > >
> > > bc more than fleeting, but not ukasian.
> > >
> > > p.s. BrianW's example: counter thought:  more coulomb and less
> > > viscous / turbulent?  (greater normal force, M*V^2/R ?)
> > >
> > >
> > > On 2009, Jul 16, , at 04:44, Brian Whatcott wrote:
> > >       
> > > > I had some fleeting thought that the vertical speed profile with body
> > > > mass ought to be
> > > > reasonably constant, but the acceleration round the tight curves would
> > > > be more
> > > >  forceful to a heavier adult?
> > > > BrianW
> > > >
> > > > Bernard Cleyet wrote:
> > > >         
> > > > > Is there any reason to believe a child doesn't come close to the lip?
> > > > >
> > > > > bc's  only big experience is the one usta be at alum rock park, San
> > > > > Jose.
> > > > >
> > > > > p.s.  Now I think gone due to CalOSHA.  A rather tame one in the
> > > > > municipal pool in Gavle or Sandviken  (Sweden).
> > > > >
> > > > >
> > > > > On 2009, Jul 13, , at 09:24, Brian Whatcott wrote:
> > > > >           
> > > > > > This adult felt like he was coming quite close to the lip....
> > > > > >             
I evidently have gone blind to this basic concept.
If I visualize a slide that is straight in plan, then I expect to exit 
with a velocity v
neglecting friction, of magnitude given by root 2gh. The vertical force 
would have been provided by a diluted gravity, en route, with an exit 
following a somewhat greater than 1g 'gravity'.
If a horizontal half tube torus is tacked onto this exit, I expect to 
feel an additional force - call it central reaction in my moving frame.  
so the force diagram would amount to mg vertically and mv^2 / r horizontally
for r the radius of the horizontal torus. The centers of gravity of a 
child and adult would experience the same amount of tilted "gravity"  so 
both would  feel the same angle of tilt. The adult being wider  would 
approach closer to the rim (if it were a torus sliced on a horizontal 
diameter at least) but how could a child avoid feeling the same extra 
component from the horizontal rotation, where the straight plan-view slide
would offer less total "gravity" forces. Surely a child should also 
prefer the straight slide as "less scary".
If not, why not?   :-)

Brian W