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We show that quantized magnetic vortex lattice in high-temperature cuprate superconductors driven by dc or ac current is a very good model system for investigating physics of friction of solid. Based on the dc I-V characteristic measurement and viscosity measurement using microwave techniques in Bi₂Sr₂CaCu₂O_y and La_1.85Sr_0.15CuO₄, the corresponding kinetic friction was obtained as functions of temperature, magnetic field and driving current density. With increasing magnetic field and temperature, velocity dependence of kinetic friction behaves as that at interfaces with weak interaction of solid. This result means that we can control the kinetic friction, and that systematic experiments are available in a reproducible manner with using this system. Behavior of the kinetic friction at higher velocities (~1 km/s) agrees well with a two-class potential model at finite temperatures. Irradiation of the columnar defects was found to move the system closer to the so-called Amontons-Coulomb friction. This suggests that the random potential created by the strong pinning centers plays an important role of the validity of Amontons-Coulomb law.

Computational modeling methods were used to explore how well the behavior of a surface with a micropatterned array of uniformly shaped and spaced semi-cylindrical ribs, as predicted through a deterministic model, may be represented using a traditional Coulomb-based bulk-effects friction model. The effects of the numerical solution method, contact enforcement method, material damage model, and the number of asperities considered were first examined when the micropatterned ribs were directly included in the computational domain. The tribological behavior, defined as the static and kinetic friction forces and the associated energy dissipated, was then recreated for a comparable smooth-surface system using a Coulomb-based bulk-effects friction model, exploring the influence of user-input parameters such as the friction coefficients. With properly selected bulk-effects model parameters, the tribological behavior could be matched between the two types of models. However, the bulk-effects model could not capture the local and time-dependent effects of the asperity interactions on the force and energy measures, which are important in designing micropatterned surfaces. Through the understanding of the influences on model function that is gained through this work, a means to determine the appropriateness of each of these interface model types in studying particular phenomena of interest is provided.

Recently, the use of video analysis technique has emerged as an effective and facile learning tool, due to the richness of spatial and temporal data useful to investigate the complex physical phenomena related to kinematics. In this study, we have investigated the motion of solid and annular cylinders rolling down an inclined wooden plane at different angles. The linear accelerations of the cylinders for the case of rolling (with and without slipping) have been derived theoretically and have been compared with their experimental counterparts. Specifically, the experimental values have been determined by performing a series of experiments, wherein the motion of the cylinders has been captured via a digital camera (recording at 240 frames s${}^{-1}$) and later analyzed frame by frame utilizing in-house developed GUI-based “Phystrack” video tracking library. We have measured the transition angles corresponding to the transition of motion (a) from rest to rolling, and (b) from pure rolling to a combination of rolling and slipping mode of motion, for the case of two distinct cylinders. This has eventually allowed us to compute the coefficient of static, kinetic and rolling friction for the aforementioned cylinders. In general, the coefficient of kinetic friction is regarded as an intrinsic material-dependent constant and considered as independent of the geometry of the object. However, in the case of rolling motion, the coefficients of friction are strongly dependent upon the geometrical parameters of the rolling object. The study emphasizes on developing the conceptual understanding ability of physics students pertaining to the friction coefficient of rolling objects.