Kolinski, John M.Aussillous, PascaleMahadevan, L.2019-09-262009Kolinski, John M., Pascale Aussillous, and L. Mahadevan. 2009. “Shape and Motion of a Ruck in a Rug.” Physical Review Letters 103 (17). https://doi.org/10.1103/physrevlett.103.174302.0031-90071079-71141092-0145http://nrs.harvard.edu/urn-3:HUL.InstRepos:41412232The motion of a ruck in a rug is used as an analogy to explain the role of dislocations in crystalline solids. We take literally one side of this analogy and study the shape and motion of a bump, wrinkle or ruck in a thin sheet in partial contact with a rough substrate in a gravitational field. Using a combination of experiments, scaling analysis and numerical solutions of the governing equations, we quantify the static shape of a ruck on a horizontal plane. When the plane is inclined, the ruck becomes asymmetric and moves by rolling only when the inclination of the plane reaches a critical angle, at a speed determined by a simple power balance. We find that the angle at which rolling starts is larger than the angle at which the ruck stops; i.e., static rolling friction is larger than dynamic rolling friction. We conclude with a generalization of our results to wrinkles in soft adherent extensible films.en-USJournal Article2019-09-2610.1103/PhysRevLett.103.174302