text: A model of this phenomenon developed in Lund and Grenoble built on an earlier one that analogized its relation with position to a stress-strain curve and accounted for hysteresis in the case of permanent displacement.
full_question: A model of this phenomenon developed in Lund and Grenoble built on an earlier one that analogized its relation with position to a stress-strain curve and accounted for hysteresis in the case of permanent displacement. Described by the Dahl model, this behavior was shown by IBM in 2008 at a molecular level using an atomic force microscope on cobalt atoms cooled to 5K. This phenomenon causes head loss proportional to the flow velocity squared divided by the hydraulic diameter and multiplied by the pipe length as well as a value describing this phenomenon named for Darcy. The strength of this force is independent of contact area and sliding velocity according to laws named for Amontons and Coulomb. For 10 points, name this force whose maximum value is proportional to the normal force and which opposes motion.
first_sentence: A model of this phenomenon developed in Lund and Grenoble built on an earlier one that analogized its relation with position to a stress-strain curve and accounted for hysteresis in the case of permanent displacement.
raw_answer: friction