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SUMMARY:An Introduction to the Mechanics of the Lasso - Neil Ribe (CNRS (C
 entre national de la recherche scientifique)\; Université Paris Saclay)
DTSTART:20171130T160000Z
DTEND:20171130T163000Z
UID:TALK96169@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:<span>Co-authors: Pierre-Thomas Brun		(Dept. of Chemical Engin
 eering\, Princeton University\, Princeton\, NJ USA)\, Basile Audoly		(Labo
 ratoire LMS\, Ecole Polytechnique\, Palaiseau\, France)        <br></span>
 <span><br>Trick roping evolved from humble origins as a cattle-catching to
 ol into a sport that delights audiences with its complex patterns or &lsqu
 o\;tricks&rsquo\;. Its fundamental tool is the lasso\, formed by passing o
 ne end of a rope through a small loop (the honda) at the other end. Here\,
  we study the mechanics of the simplest rope trick\, the Flat Loop\, in wh
 ich the rope is driven by the steady circular motion of the roper&rsquo\;s
  hand in a horizontal plane. We first consider the case of a fixed (non-sl
 iding) honda. Noting that the rope&rsquo\;s shape is steady in the referen
 ce frame rotating with the hand\, we analyse a string model in which line 
 tension is balanced by the centrifugal force and the rope&rsquo\;s weight.
  We use numerical continuation to classify the steadily rotating solutions
  in a bifurcation diagram and analyse their stability. In addition to Flat
  Loops\, we find planar &lsquo\;coat-hanger&rsquo\; solutions\, and whirli
 ng modes in which the loop collapses onto itself. Ne xt\, we treat the mor
 e general case of a honda that can slide due to a finite coefficient of fr
 iction of the rope on itself. Using matched asymptotic expansions\, we res
 olve the shape of the rope in the boundary layer near the honda where the 
 rope&rsquo\;s bending stiffness cannot be neglected. We use this solution 
 to derive a macroscopic criterion for the sliding of the honda in terms of
  the microscopic Coulomb static friction criterion. Our predictions agree 
 well with rapid- camera observations of a professional trick roper and wit
 h laboratory experiments using a &lsquo\;robo-cowboy&rsquo\;.</span>
LOCATION:Seminar Room 1\, Newton Institute
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