Re: [Phys-l] Static vs kinetic friction

[Bernard Cleyet <bernardcleyet@redshift.com>]

Adding to my yesterday's post***,

I have since found some graphs of the cart both driven and not.

Interested may apply.

bc


***
> So can the kicked cart stop during
> the turnaround because of this effect?


I have observed this often and I suspect many others.  For example a
mechanical oscillator with Coulomb friction will stop at an other
than the equilibrium position.

I have attached a cart friction accessory to a driven cart acting as
the mass of a spring oscillator.   The driver was an attached (as the
support) high Q and energetic pendulum.  The effect is quite
interesting.  As the pendulum decays (rings down) the delay in the
movement of the periodically stopped cart increases.  Since I don't
have a site, I refer to Peter's flip-flop pendulum for the analysis
of a similar pendulum

http://adsabs.harvard.edu/abs/1997AmJPh..65.1067P


bc will send a PDF attachment for those unable to access.




On 2009, Oct 13, , at 11:04, Carl Mungan wrote:

> > Does static friction come into play during the instant when a cart  
> > reverses
> > direction after being kicked up the ramp?
>
> While recognizing that experimental variability can be substantial,
> at least within the context of our simplified model of friction, the
> answer is clearly yes:
>
> Choose the angle of the ramp to be between the inverse tangent of the
> kinetic and static coefficients.
>
> So for best chance of experimental success, choose some pair of
> surfaces where the difference between the static and kinetic
> coefficients is large (and probably where the kinetic value is quite
> small so that the ramp angle won't be unmanageably large).
> --
> Carl E Mungan, Assoc Prof of Physics  410-293-6680 (O) -3729 (F)
> Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363
> mailto:mungan@usna.edu     http://usna.edu/Users/physics/mungan/
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